diff --git a/.openpublishing.redirection.csharp.json b/.openpublishing.redirection.csharp.json
index 25c1563e1f38b..e9be684712504 100644
--- a/.openpublishing.redirection.csharp.json
+++ b/.openpublishing.redirection.csharp.json
@@ -310,6 +310,10 @@
       "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs0417.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/generic-type-parameters-errors"
     },
+    {
+      "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs0446.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
     {
       "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs0467.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/lambda-expression-errors"
@@ -438,6 +442,10 @@
       "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs1564.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/invalid-build-command-line"
     },
+    {
+      "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs1579.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
     {
       "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs1614.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/attribute-usage-errors"
@@ -446,6 +454,10 @@
       "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs1616.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/invalid-build-command-line"
     },
+    {
+      "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs1640.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
     {
       "source_path_from_root": "/docs/csharp/language-reference/compiler-messages/cs1656.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/unsafe-code-errors"
@@ -1848,6 +1860,10 @@
       "source_path_from_root": "/docs/csharp/misc/cs0200.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/property-declaration-errors"
     },
+    {
+      "source_path_from_root": "/docs/csharp/misc/cs0202.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
     {
       "source_path_from_root": "/docs/csharp/misc/cs0206.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/ref-modifiers-errors"
@@ -1912,6 +1928,10 @@
       "source_path_from_root": "/docs/csharp/misc/cs0227.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/unsafe-code-errors"
     },
+    {
+      "source_path_from_root": "/docs/csharp/misc/cs0230.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
     {
       "source_path_from_root": "/docs/csharp/misc/cs0231.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/params-arrays"
@@ -1988,6 +2008,18 @@
       "source_path_from_root": "/docs/csharp/misc/cs0277.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/interface-implementation-errors"
     },
+    {
+      "source_path_from_root": "/docs/csharp/misc/cs0278.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
+    {
+      "source_path_from_root": "/docs/csharp/misc/cs0279.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
+    {
+      "source_path_from_root": "/docs/csharp/misc/cs0280.md",
+      "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/foreach-diagnostics"
+    },
     {
       "source_path_from_root": "/docs/csharp/misc/cs0282.md",
       "redirect_url": "/dotnet/csharp/language-reference/compiler-messages/partial-declarations"
diff --git a/docs/csharp/language-reference/compiler-messages/cs0446.md b/docs/csharp/language-reference/compiler-messages/cs0446.md
deleted file mode 100644
index 8291d78372202..0000000000000
--- a/docs/csharp/language-reference/compiler-messages/cs0446.md
+++ /dev/null
@@ -1,33 +0,0 @@
----
-description: "Compiler Error CS0446"
-title: "Compiler Error CS0446"
-ms.date: 07/20/2015
-f1_keywords: 
-  - "CS0446"
-helpviewer_keywords: 
-  - "CS0446"
-ms.assetid: d7a07e24-722e-484d-b6d7-ca809b51858f
----
-# Compiler Error CS0446
-
-Foreach cannot operate on a 'Method or Delegate'. Did you intend to invoke the 'Method or Delegate'?  
-  
- This error is caused by specifying a method without parentheses or an anonymous method without parentheses in the part of the `foreach` statement where you would normally put a collection class. Note that it is valid, though unusual, to put a method call in that location, if the method returns a collection class.  
-  
-## Example  
-
- The following code will generate CS0446.  
-  
-```csharp  
-// CS0446.cs  
-using System;  
-class Tester
-{  
-    static void Main()
-    {  
-        int[] intArray = new int[5];  
-        foreach (int i in M) { } // CS0446  
-    }  
-    static void M() { }  
-}  
-```
diff --git a/docs/csharp/language-reference/compiler-messages/cs1579.md b/docs/csharp/language-reference/compiler-messages/cs1579.md
deleted file mode 100644
index 07814fab8df20..0000000000000
--- a/docs/csharp/language-reference/compiler-messages/cs1579.md
+++ /dev/null
@@ -1,74 +0,0 @@
----
-description: "Compiler Error CS1579"
-title: "Compiler Error CS1579"
-ms.date: 05/24/2018
-f1_keywords: 
-  - "CS1579"
-helpviewer_keywords: 
-  - "CS1579"
-ms.assetid: 1eba84ce-58df-4fe3-9134-e26efefdc4ab
----
-# Compiler Error CS1579
-
-foreach statement cannot operate on variables of type 'type1' because 'type2' does not contain a public definition for 'identifier'
-
-To iterate through a collection using the [foreach](../statements/iteration-statements.md#the-foreach-statement) statement, the collection must meet the following requirements:
-
-- Its type must include a public parameterless `GetEnumerator` method whose return type is either class, struct, or interface type.
-- The return type of the `GetEnumerator` method must contain a public property named `Current` and a public parameterless method named `MoveNext` whose return type is <xref:System.Boolean>.
-
-## Example
-
-The following sample generates CS1579 because the `MyCollection` class doesn't contain the public `GetEnumerator` method:
-
-```csharp  
-// CS1579.cs  
-using System;  
-public class MyCollection
-{  
-   int[] items;  
-   public MyCollection()
-   {  
-      items = new int[5] {12, 44, 33, 2, 50};  
-   }  
-  
-   // Delete the following line to resolve.  
-   MyEnumerator GetEnumerator()  
-  
-   // Uncomment the following line to resolve:  
-   // public MyEnumerator GetEnumerator()
-   {  
-      return new MyEnumerator(this);  
-   }  
-  
-   // Declare the enumerator class:  
-   public class MyEnumerator
-   {  
-      int nIndex;  
-      MyCollection collection;  
-      public MyEnumerator(MyCollection coll)
-      {  
-         collection = coll;  
-         nIndex = -1;  
-      }  
-  
-      public bool MoveNext()
-      {  
-         nIndex++;  
-         return (nIndex < collection.items.Length);  
-      }  
-  
-      public int Current => collection.items[nIndex];
-   }  
-  
-   public static void Main()
-   {  
-      MyCollection col = new MyCollection();  
-      Console.WriteLine("Values in the collection are:");  
-      foreach (int i in col)   // CS1579  
-      {  
-         Console.WriteLine(i);  
-      }  
-   }  
-}  
-```
diff --git a/docs/csharp/language-reference/compiler-messages/cs1640.md b/docs/csharp/language-reference/compiler-messages/cs1640.md
deleted file mode 100644
index e8132b01560cb..0000000000000
--- a/docs/csharp/language-reference/compiler-messages/cs1640.md
+++ /dev/null
@@ -1,57 +0,0 @@
----
-description: "Compiler Error CS1640"
-title: "Compiler Error CS1640"
-ms.date: 07/20/2015
-f1_keywords: 
-  - "CS1640"
-helpviewer_keywords: 
-  - "CS1640"
-ms.assetid: 1393668e-05e9-4dc2-9203-3d9c2933406f
----
-# Compiler Error CS1640
-
-foreach statement cannot operate on variables of type 'type' because it implements multiple instantiations of 'interface', try casting to a specific interface instantiation  
-  
- The type inherits from two or more instances of IEnumerator\<T>, which means there is not a unique enumeration of the type that `foreach` could use. Specify the type of IEnumerator\<T> or use another looping construct.  
-  
-## Example  
-
- The following sample generates CS1640:  
-  
-```csharp  
-// CS1640.cs  
-  
-using System;  
-using System.Collections;  
-using System.Collections.Generic;  
-  
-public class C : IEnumerable, IEnumerable<int>, IEnumerable<string>  
-{  
-    IEnumerator<int> IEnumerable<int>.GetEnumerator()  
-    {  
-        yield break;  
-    }  
-  
-    IEnumerator<string> IEnumerable<string>.GetEnumerator()  
-    {  
-        yield break;  
-    }  
-  
-    IEnumerator IEnumerable.GetEnumerator()  
-    {  
-        return (IEnumerator)((IEnumerable<string>)this).GetEnumerator();  
-    }  
-}  
-  
-public class Test  
-{  
-    public static int Main()  
-    {  
-        foreach (int i in new C()){}    // CS1640  
-  
-        // Try specifying the type of IEnumerable<T>  
-        // foreach (int i in (IEnumerable<int>)new C()){}  
-        return 1;  
-    }  
-}  
-```
diff --git a/docs/csharp/language-reference/compiler-messages/foreach-diagnostics.md b/docs/csharp/language-reference/compiler-messages/foreach-diagnostics.md
new file mode 100644
index 0000000000000..b09f32813c884
--- /dev/null
+++ b/docs/csharp/language-reference/compiler-messages/foreach-diagnostics.md
@@ -0,0 +1,159 @@
+---
+title: "Resolve errors and warnings related to async enumerables, enumerables, and `foreach` statements"
+description: "This article helps you diagnose and correct compiler errors and warnings related to async enumerables, enumerables, and foreach statements"
+f1_keywords:
+  - "CS0202"
+  - "CS0230"
+  - "CS0278"
+  - "CS0279"
+  - "CS0280"
+  - "CS0446"
+  - "CS1579"
+  - "CS1640"
+  - "CS8186"
+  - "CS8412"
+  - "CS8413"
+  - "CS8414"
+  - "CS8415"
+  - "CS8419"
+  - "CS8420"
+  - "CS8424"
+  - "CS8425"
+  - "CS8426"
+  - "CS9353"
+helpviewer_keywords:
+  - "CS0202"
+  - "CS0230"
+  - "CS0278"
+  - "CS0279"
+  - "CS0280"
+  - "CS0446"
+  - "CS1579"
+  - "CS1640"
+  - "CS8186"
+  - "CS8412"
+  - "CS8413"
+  - "CS8414"
+  - "CS8415"
+  - "CS8419"
+  - "CS8420"
+  - "CS8424"
+  - "CS8425"
+  - "CS8426"
+  - "CS9353"
+ms.date: 07/13/2026
+ai-usage: ai-assisted
+---
+
+# Resolve errors and warnings for `foreach` statements and async enumerables
+
+This article covers the following compiler errors and warnings:
+
+<!-- The text in this list generates issues for Acrolinx, because they don't use contractions.
+That's by design. The text closely matches the text of the compiler error / warning for SEO purposes.
+ -->
+
+- [**CS0202**](#enumerable-pattern-requirements): *foreach requires that the return type 'type' of 'type.GetEnumerator()' must have a suitable public 'MoveNext' method and public 'Current' property*
+- [**CS0230**](#foreach-statement-syntax): *Type and identifier are both required in a foreach statement*
+- [**CS0278**](#enumerable-pattern-requirements): *'type' does not implement the 'pattern name' pattern. 'method name' is ambiguous with 'method name'.*
+- [**CS0279**](#enumerable-pattern-requirements): *'type' does not implement the 'pattern name' pattern. 'method name' is not a public instance or extension method.*
+- [**CS0280**](#enumerable-pattern-requirements): *'type' does not implement the 'pattern name' pattern. 'method name' has the wrong signature.*
+- [**CS0446**](#foreach-statement-syntax): *Foreach cannot operate on a 'method group'. Did you intend to invoke the 'method group'?*
+- [**CS1579**](#enumerable-pattern-requirements): *foreach statement cannot operate on variables of type 'type' because 'type' does not contain a public instance or extension definition for 'member'*
+- [**CS1640**](#multiple-enumerable-implementations): *foreach statement cannot operate on variables of type 'type' because it implements multiple instantiations of 'interface'; try casting to a specific interface instantiation*
+- [**CS8186**](#foreach-statement-syntax): *A foreach loop must declare its iteration variables.*
+- [**CS8412**](#enumerable-pattern-requirements): *Asynchronous foreach requires that the return type 'type' of 'method' must have a suitable public 'MoveNextAsync' method and public 'Current' property*
+- [**CS8413**](#multiple-enumerable-implementations): *Asynchronous foreach statement cannot operate on variables of type 'type' because it implements multiple instantiations of 'interface'; try casting to a specific interface instantiation*
+- [**CS8414**](#mismatched-foreach-and-await-foreach): *foreach statement cannot operate on variables of type 'type' because 'type' does not contain a public instance or extension definition for 'member'. Did you mean 'await foreach' rather than 'foreach'?*
+- [**CS8415**](#mismatched-foreach-and-await-foreach): *Asynchronous foreach statement cannot operate on variables of type 'type' because 'type' does not contain a public instance or extension definition for 'member'. Did you mean 'foreach' rather than 'await foreach'?*
+- [**CS8419**](#async-iterator-method-body): *The body of an async-iterator method must contain a 'yield' statement.*
+- [**CS8420**](#async-iterator-method-body): *The body of an async-iterator method must contain a 'yield' statement. Consider removing 'async' from the method declaration or adding a 'yield' statement.*
+- [**CS8424**](#enumeratorcancellation-attribute-usage): *The EnumeratorCancellationAttribute applied to parameter 'name' will have no effect. The attribute is only effective on a parameter of type CancellationToken in an async-iterator method returning IAsyncEnumerable*
+- [**CS8425**](#enumeratorcancellation-attribute-usage): *Async-iterator 'method' has one or more parameters of type 'CancellationToken' but none of them is decorated with the 'EnumeratorCancellation' attribute, so the cancellation token parameter from the generated 'IAsyncEnumerable<>.GetAsyncEnumerator' will be unconsumed*
+- [**CS8426**](#enumeratorcancellation-attribute-usage): *The attribute [EnumeratorCancellation] cannot be used on multiple parameters*
+- [**CS9353**](#mismatched-foreach-and-await-foreach): *'type' does not contain a definition for 'member' and no accessible extension method 'member' accepting a first argument of type 'type' could be found (did you mean to iterate over the async collection with 'await foreach' instead?)*
+
+## `foreach` statement syntax
+
+- **CS0230**: *Type and identifier are both required in a foreach statement*
+- **CS0446**: *Foreach cannot operate on a 'method group'. Did you intend to invoke the 'method group'?*
+- **CS8186**: *A foreach loop must declare its iteration variables.*
+
+These errors indicate that the [`foreach` statement](../statements/iteration-statements.md#the-foreach-statement) itself is malformed, regardless of whether the collection type is valid.
+
+Declare both a type (or `var`) and an identifier for the iteration variable (**CS0230**, **CS8186**). The `foreach` statement requires a loop variable declaration. You can't omit either the type or the name. For example, write `foreach (int x in collection)` rather than `foreach (int in collection)`.
+
+Invoke the method or delegate rather than passing it as a collection expression (**CS0446**). If you reference a method group or delegate without parentheses in the `in` clause, the compiler reports this error because it expects a collection value. Add parentheses to call the method, provided it returns an enumerable type: `foreach (var item in GetItems())`.
+
+## Enumerable pattern requirements
+
+- **CS0202**: *foreach requires that the return type 'type' of 'type.GetEnumerator()' must have a suitable public 'MoveNext' method and public 'Current' property*
+- **CS0278**: *'type' does not implement the 'pattern name' pattern. 'method name' is ambiguous with 'method name'.*
+- **CS0279**: *'type' does not implement the 'pattern name' pattern. 'method name' is not a public instance or extension method.*
+- **CS0280**: *'type' does not implement the 'pattern name' pattern. 'method name' has the wrong signature.*
+- **CS1579**: *foreach statement cannot operate on variables of type 'type' because 'type' does not contain a public instance or extension definition for 'member'*
+- **CS8412**: *Asynchronous foreach requires that the return type 'type' of 'method' must have a suitable public 'MoveNextAsync' method and public 'Current' property*
+
+The `foreach` statement uses a pattern-based approach rather than requiring a specific interface. For a type to be enumerable, it must provide:
+
+- A public parameterless `GetEnumerator` method (or `GetAsyncEnumerator` for `await foreach`) whose return type is a class, struct, or interface.
+- On the enumerator return type: a public `Current` property and a public parameterless `MoveNext` method returning `bool` (or a public parameterless `MoveNextAsync` method that returns `Task<bool>`, `ValueTask<bool>`, or any other awaitable type whose awaiter's `GetResult` method returns a `bool` value).
+For details on the enumerable pattern, see [Iteration statements - `foreach`](../statements/iteration-statements.md#the-foreach-statement).
+
+Ensure `GetEnumerator` returns a proper enumerator type — not an array or pointer (**CS0202**). The return value must be a type that itself exposes `MoveNext` and `Current`.
+
+Add a public `GetEnumerator` method if the type doesn't have one (**CS1579**). Alternatively, implement <xref:System.Collections.Generic.IEnumerable%601> or provide an extension method named `GetEnumerator`. For `await foreach`, provide `GetAsyncEnumerator` or implement <xref:System.Collections.Generic.IAsyncEnumerable%601>.
+
+Ensure that `GetAsyncEnumerator` returns a type with a public `Current` property and a public parameterless `MoveNextAsync` method that returns `Task<bool>`, `ValueTask<bool>`, or any other awaitable type whose awaiter's `GetResult` method returns a `bool` value (**CS8412**). This is the async equivalent of **CS0202**.
+
+Resolve ambiguity when multiple methods match the pattern name (**CS0278**). This warning occurs when the compiler finds two candidates for `MoveNext` or `GetEnumerator`. Remove or rename the conflicting member, or cast to a specific interface to disambiguate.
+
+Make pattern methods public and non-static (**CS0279**). The enumerable pattern requires that `GetEnumerator`, `MoveNext`, and `Current` be public instance members (or public extension methods). Change `internal` or `static` members to `public` instance members.
+
+Correct the signature of pattern methods (**CS0280**). For example, `MoveNext` must take no parameters and return `bool`. If a field or property shadows the method name, rename it so the compiler can find the correct method.
+
+## Multiple enumerable implementations
+
+- **CS1640**: *foreach statement cannot operate on variables of type 'type' because it implements multiple instantiations of 'interface'; try casting to a specific interface instantiation*
+- **CS8413**: *Asynchronous foreach statement cannot operate on variables of type 'type' because it implements multiple instantiations of 'interface'; try casting to a specific interface instantiation*
+
+These errors occur when the collection type implements multiple generic instantiations of <xref:System.Collections.Generic.IEnumerable%601> (**CS1640**) or <xref:System.Collections.Generic.IAsyncEnumerable%601> (**CS8413**), creating ambiguity about which element type to enumerate.
+
+Cast the collection to a specific interface instantiation before iterating. For example, if a type implements both `IEnumerable<int>` and `IEnumerable<string>`, write `foreach (int i in (IEnumerable<int>)collection)` to select the desired element type.
+
+## Mismatched `foreach` and `await foreach`
+
+- **CS8414**: *foreach statement cannot operate on variables of type 'type' because 'type' does not contain a public instance or extension definition for 'member'. Did you mean 'await foreach' rather than 'foreach'?*
+- **CS8415**: *Asynchronous foreach statement cannot operate on variables of type 'type' because 'type' does not contain a public instance or extension definition for 'member'. Did you mean 'foreach' rather than 'await foreach'?*
+- **CS9353**: *'type' does not contain a definition for 'member' and no accessible extension method 'member' accepting a first argument of type 'type' could be found (did you mean to iterate over the async collection with 'await foreach' instead?)*
+
+These errors indicate a mismatch between the kind of `foreach` statement and the interfaces the collection type implements.
+
+Use `await foreach` instead of `foreach` when the collection implements only <xref:System.Collections.Generic.IAsyncEnumerable%601> (**CS8414**, **CS9353**). Async-enumerable types provide `GetAsyncEnumerator` rather than `GetEnumerator`, so you must use `await foreach` in an `async` method to iterate them.
+
+Use `foreach` instead of `await foreach` when the collection implements only <xref:System.Collections.Generic.IEnumerable%601> (**CS8415**). Synchronous collections don't provide `GetAsyncEnumerator`, so `await foreach` can't enumerate them.
+
+## Async iterator method body
+
+- **CS8419**: *The body of an async-iterator method must contain a 'yield' statement.*
+- **CS8420**: *The body of an async-iterator method must contain a 'yield' statement. Consider removing 'async' from the method declaration or adding a 'yield' statement.*
+
+These errors occur when a method's signature declares it as an async iterator (it's `async` and returns <xref:System.Collections.Generic.IAsyncEnumerable%601> or <xref:System.Collections.Generic.IAsyncEnumerator%601>) but the body contains no `yield return` or `yield break` statement.
+
+Add at least one `yield return` statement to the method body to make it a valid async-iterator method. If you didn't intend the method to be an iterator, remove the `async` modifier and change the return type, or return a constructed async enumerable from a different source instead.
+
+For more information on iterator methods, see [Iterators](../../iterators.md) and [`yield` statement](../statements/yield.md).
+
+## `EnumeratorCancellation` attribute usage
+
+- **CS8424**: *The EnumeratorCancellationAttribute applied to parameter 'name' will have no effect. The attribute is only effective on a parameter of type CancellationToken in an async-iterator method returning IAsyncEnumerable*
+- **CS8425**: *Async-iterator 'method' has one or more parameters of type 'CancellationToken' but none of them is decorated with the 'EnumeratorCancellation' attribute, so the cancellation token parameter from the generated 'IAsyncEnumerable<>.GetAsyncEnumerator' will be unconsumed*
+- **CS8426**: *The attribute [EnumeratorCancellation] cannot be used on multiple parameters*
+
+These diagnostics relate to the <xref:System.Runtime.CompilerServices.EnumeratorCancellationAttribute>, which connects a <xref:System.Threading.CancellationToken> parameter to the token supplied by <xref:System.Collections.Generic.IAsyncEnumerable%601.GetAsyncEnumerator(System.Threading.CancellationToken)>.
+
+Apply `[EnumeratorCancellation]` only to a parameter of type <xref:System.Threading.CancellationToken> in an async-iterator method that returns <xref:System.Collections.Generic.IAsyncEnumerable%601> (**CS8424**). The attribute has no effect in any other context, such as non-token parameters, non-iterator methods, or methods returning other types.
+
+Add the `[EnumeratorCancellation]` attribute to exactly one `CancellationToken` parameter (**CS8425**). Without this attribute, the token provided by callers through `WithCancellation` isn't forwarded to the iterator body. The generated `GetAsyncEnumerator(CancellationToken)` parameter goes unconsumed.
+
+Apply the attribute to only one parameter, not multiple (**CS8426**). The runtime infrastructure supports forwarding a single cancellation token to the iterator. If you have multiple token parameters, designate only one with the attribute and combine others manually using <xref:System.Threading.CancellationTokenSource.CreateLinkedTokenSource(System.Threading.CancellationToken,System.Threading.CancellationToken)>.
diff --git a/docs/csharp/language-reference/toc.yml b/docs/csharp/language-reference/toc.yml
index 5c871285af4ec..1654d4c4eb8df 100644
--- a/docs/csharp/language-reference/toc.yml
+++ b/docs/csharp/language-reference/toc.yml
@@ -495,13 +495,14 @@ items:
   - name: Feature or version missing
     href: ./compiler-messages/feature-version-errors.md
     displayName: >
-      CS0171, CS0188, CS0843, CS1617, CS1638, CS1738, CS8021, CS8022, CS8023, CS8024, CS8025, CS8026,
-      CS8058, CS8059, CS8107, CS8192, CS8302, CS8303, CS8304, CS8305, CS8306, CS8314,
-      CS8320, CS8370, CS8371, CS8400, CS8401, CS8511, CS8627, CS8630, CS8652, CS8701,
-      CS8702, CS8703, CS8704, CS8706, CS8707, CS8773, CS8830, CS8831, CS8888, CS8889,
-      CS8890, CS8891, CS8904, CS8912, CS8919, CS8929, CS8936, CS8957, CS8967, CS9014,
-      CS9015, CS9016, CS9017, CS9041, CS9058, CS9064, CS9103, CS9171, CS9194, CS9202,
-      CS9204, CS9240, CS9260, CS9268, CS9269, CS9271, CS9327, CS9328, CS9346, CS9352
+      CS0171, CS0188, CS0843, CS1617, CS1638, CS1738, CS8021, CS8022, CS8023, CS8024,
+      CS8025, CS8026, CS8058, CS8059, CS8107, CS8192, CS8302, CS8303, CS8304, CS8305,
+      CS8306, CS8314, CS8320, CS8370, CS8371, CS8400, CS8401, CS8511, CS8627, CS8630,
+      CS8652, CS8701, CS8702, CS8703, CS8704, CS8706, CS8707, CS8773, CS8830, CS8831,
+      CS8888, CS8889, CS8890, CS8891, CS8904, CS8912, CS8919, CS8929, CS8936, CS8957,
+      CS8967, CS9014, CS9015, CS9016, CS9017, CS9041, CS9058, CS9064, CS9103, CS9171,
+      CS9194, CS9202, CS9204, CS9240, CS9260, CS9268, CS9269, CS9271, CS9327, CS9328,
+      CS9346, CS9352
   - name: Assembly references
     href: ./compiler-messages/assembly-references.md
     displayName: >
@@ -622,6 +623,12 @@ items:
       yield return, yield break,
       CS1622, CS1624, CS1625, CS1626, CS1627, CS1629, CS1631, CS1637, CS4013, CS8154,
       CS8176, CS9237, CS9238, CS9239
+  - name: foreach statements and async enumerables
+    href: ./compiler-messages/foreach-diagnostics.md
+    displayName: >
+      foreach, await foreach, async enumerable, GetAsyncEnumerator, IAsyncEnumerable,
+      CS0202, CS0230, CS0278, CS0279, CS0280, CS0446, CS1579, CS1640, CS8186, CS8412,
+      CS8413, CS8414, CS8415, CS8419, CS8420, CS8424, CS8425, CS8426, CS9353
   - name: Extension declarations
     href: ./compiler-messages/extension-declarations.md
     displayName: >
@@ -687,11 +694,11 @@ items:
   - name: Lambda expressions
     href: ./compiler-messages/lambda-expression-errors.md
     displayName: >
-      CS0407, CS0428, CS0467, CS0748, CS0815, CS0828, CS0837, CS1065, CS1621, CS1628, CS1632,
-      CS1643, CS1660, CS1661, CS1662, CS1673, CS1676, CS1677, CS1678, CS1686, CS1688,
-      CS1706, CS1731, CS1732, CS1764, CS1911, CS1989, CS3006, CS8030, CS8175, CS8820,
-      CS8821, CS8916, CS8917, CS8934, CS8971, CS8972, CS8974, CS8975, CS9098, CS9099,
-      CS9100, CS9236
+      CS0407, CS0428, CS0467, CS0748, CS0815, CS0828, CS0837, CS1065, CS1621, CS1628,
+      CS1632, CS1643, CS1660, CS1661, CS1662, CS1673, CS1676, CS1677, CS1678, CS1686,
+      CS1688, CS1706, CS1731, CS1732, CS1764, CS1911, CS1989, CS3006, CS8030, CS8175,
+      CS8820, CS8821, CS8916, CS8917, CS8934, CS8971, CS8972, CS8974, CS8975, CS9098,
+      CS9099, CS9100, CS9236
   - name: Delegate and function pointer declarations
     href: ./compiler-messages/delegate-function-pointer-diagnostics.md
     displayName: >
@@ -715,11 +722,11 @@ items:
   - name: Using directive and aliases
     href: ./compiler-messages/using-directive-errors.md
     displayName: >
-      CS0104, CS0105, CS0116, CS0138, CS0430, CS0431, CS0432, CS0434, CS0435, CS0436, CS0437,
-      CS0438, CS0439, CS0440, CS0518, CS0576, CS0687, CS1022, CS1529,
-      CS1537, CS1671, CS1679, CS1680, CS1681, CS1730, CS2034, CS7000, CS7007, CS7015,
-      CS7021, CS8019, CS8020, CS8083, CS8085, CS8914, CS8915, CS8933, CS8954, CS8955, CS8956, CS9130,
-      CS9131, CS9132, CS9133, CS9162
+      CS0104, CS0105, CS0116, CS0138, CS0430, CS0431, CS0432, CS0434, CS0435, CS0436,
+      CS0437, CS0438, CS0439, CS0440, CS0518, CS0576, CS0687, CS1022, CS1529, CS1537,
+      CS1671, CS1679, CS1680, CS1681, CS1730, CS2034, CS7000, CS7007, CS7015, CS7021,
+      CS8019, CS8020, CS8083, CS8085, CS8914, CS8915, CS8933, CS8954, CS8955, CS8956,
+      CS9130, CS9131, CS9132, CS9133, CS9162
   - name: Using statements and declarations
     href: ./compiler-messages/using-statement-declaration-errors.md
     displayName: >
@@ -976,12 +983,8 @@ items:
       href: ../misc/cs0191.md
     - name: CS0198
       href: ../misc/cs0198.md
-    - name: CS0200
-      href: ./compiler-messages/property-declaration-errors.md
     - name: CS0201
       href: ./compiler-messages/cs0201.md
-    - name: CS0202
-      href: ../misc/cs0202.md
     - name: CS0204
       href: ../misc/cs0204.md
     - name: CS0205
@@ -992,8 +995,6 @@ items:
       href: ../misc/cs0228.md
     - name: CS0229
       href: ./compiler-messages/cs0229.md
-    - name: CS0230
-      href: ../misc/cs0230.md
     - name: CS0236
       href: ../misc/cs0236.md
     - name: CS0238
@@ -1042,14 +1043,10 @@ items:
       href: ../misc/cs0443.md
     - name: CS0445
       href: ./compiler-messages/cs0445.md
-    - name: CS0446
-      href: ./compiler-messages/cs0446.md
     - name: CS0462
       href: ../misc/cs0462.md
     - name: CS0468
       href: ../misc/cs0468.md
-    - name: CS0470
-      href: ./compiler-messages/interface-implementation-errors.md
     - name: CS0471
       href: ../misc/cs0471.md
     - name: CS0500
@@ -1092,26 +1089,14 @@ items:
       href: ../misc/cs0534.md
     - name: CS0537
       href: ../misc/cs0537.md
-    - name: CS0538
-      href: ./compiler-messages/interface-implementation-errors.md
-    - name: CS0539
-      href: ./compiler-messages/interface-implementation-errors.md
-    - name: CS0541
-      href: ./compiler-messages/interface-implementation-errors.md
     - name: CS0542
       href: ../misc/cs0542.md
-    - name: CS0545
-      href: ./compiler-messages/property-declaration-errors.md
     - name: CS0549
       href: ../misc/cs0549.md
-    - name: CS0551
-      href: ./compiler-messages/interface-implementation-errors.md
     - name: CS0569
       href: ../misc/cs0569.md
     - name: CS0570
       href: ./compiler-messages/cs0570.md
-    - name: CS0571
-      href: ./compiler-messages/property-declaration-errors.md
     - name: CS0572
       href: ../misc/cs0572.md
     - name: CS0574
@@ -1248,8 +1233,6 @@ items:
       href: ../misc/cs0833.md
     - name: CS0836
       href: ../misc/cs0836.md
-    - name: CS0840
-      href: ./compiler-messages/property-declaration-errors.md
     - name: CS0841
       href: ../misc/cs0841.md
     - name: CS0842
@@ -1270,8 +1253,6 @@ items:
       href: ../misc/cs1010.md
     - name: CS1013
       href: ../misc/cs1013.md
-    - name: CS1014
-      href: ./compiler-messages/property-declaration-errors.md
     - name: CS1015
       href: ../misc/cs1015.md
     - name: CS1017
@@ -1292,8 +1273,6 @@ items:
       href: ../misc/cs1036.md
     - name: CS1041
       href: ../misc/cs1041.md
-    - name: CS1043
-      href: ./compiler-messages/property-declaration-errors.md
     - name: CS1044
       href: ../misc/cs1044.md
     - name: CS1055
@@ -1386,8 +1365,6 @@ items:
       href: ../misc/cs1575.md
     - name: CS1577
       href: ../misc/cs1577.md
-    - name: CS1579
-      href: ./compiler-messages/cs1579.md
     - name: CS1583
       href: ../misc/cs1583.md
     - name: CS1585
@@ -1422,12 +1399,8 @@ items:
       href: ../misc/cs1620.md
     - name: CS1630
       href: ../misc/cs1630.md
-    - name: CS1637
-      href: ./compiler-messages/iterator-yield.md
     - name: CS1639
       href: ../misc/cs1639.md
-    - name: CS1640
-      href: ./compiler-messages/cs1640.md
     - name: CS1644
       href: ./compiler-messages/cs1644.md
     - name: CS1646
@@ -1646,8 +1619,6 @@ items:
       href: ./compiler-messages/cs8355.md
     - name: CS8422
       href: ./compiler-messages/cs8422.md
-    - name: CS9036
-      href: ./compiler-messages/property-declaration-errors.md
     - name: CS9043
       href: ./compiler-messages/cs9043.md
   - name: Level 1 warning messages
@@ -1796,12 +1767,6 @@ items:
       href: ../misc/cs0252.md
     - name: CS0253
       href: ../misc/cs0253.md
-    - name: CS0278
-      href: ../misc/cs0278.md
-    - name: CS0279
-      href: ../misc/cs0279.md
-    - name: CS0280
-      href: ../misc/cs0280.md
     - name: CS0444
       href: ../misc/cs0444.md
     - name: CS0458
diff --git a/docs/csharp/misc/cs0202.md b/docs/csharp/misc/cs0202.md
deleted file mode 100644
index 4ba035827d1e6..0000000000000
--- a/docs/csharp/misc/cs0202.md
+++ /dev/null
@@ -1,81 +0,0 @@
----
-description: "Compiler Error CS0202"
-title: "Compiler Error CS0202"
-ms.date: 07/20/2015
-f1_keywords:
-  - "CS0202"
-helpviewer_keywords:
-  - "CS0202"
-ms.assetid: 7088850f-c206-4b95-9586-a0fa3d876c0c
----
-# Compiler Error CS0202
-
-foreach requires that the return type 'type' of 'type.GetEnumerator()' must have a suitable public MoveNext method and public Current property
-
- A <xref:System.Collections.IEnumerable.GetEnumerator*> function, used to enable the use of foreach statements, cannot return a pointer or array; it must return an instance of a class that is able to act as an enumerator. The proper requirements to serve as an enumerator include a public Current property and a public MoveNext method.
-
-> [!NOTE]
-> In C# 2.0, the compiler will automatically generate Current and MoveNext for you. For more information, see the code example in [Generic Interfaces](../programming-guide/generics/generic-interfaces.md).
-
- The following sample generates CS0202:
-
-```csharp
-// CS0202.cs
-
-public class C1
-{
-   public int Current
-   {
-      get
-      {
-         return 0;
-      }
-   }
-
-   public bool MoveNext ()
-   {
-      return false;
-   }
-
-   public static implicit operator C1 (int c1)
-   {
-      return 0;
-   }
-}
-
-public class C2
-{
-   public int Current
-   {
-      get
-      {
-         return 0;
-      }
-   }
-
-   public bool MoveNext ()
-   {
-      return false;
-   }
-
-   public C1[] GetEnumerator ()
-   // try the following line instead
-   // public C1 GetEnumerator ()
-   {
-      return null;
-   }
-}
-
-public class MainClass
-{
-   public static void Main ()
-   {
-      C2 c2 = new C2();
-
-      foreach (C1 x in c2)   // CS0202
-      {
-         System.Console.WriteLine(x.Current);
-      }
-   }
-}
-```
diff --git a/docs/csharp/misc/cs0230.md b/docs/csharp/misc/cs0230.md
deleted file mode 100644
index 91f3a82660a7e..0000000000000
--- a/docs/csharp/misc/cs0230.md
+++ /dev/null
@@ -1,50 +0,0 @@
----
-description: "Compiler Error CS0230"
-title: "Compiler Error CS0230"
-ms.date: 07/20/2015
-f1_keywords: 
-  - "CS0230"
-helpviewer_keywords: 
-  - "CS0230"
-ms.assetid: 132e4623-d393-4a5f-a3f8-838a1bfbd1b3
----
-# Compiler Error CS0230
-
-Type and identifier are both required in a foreach statement  
-  
- A [foreach](../language-reference/statements/iteration-statements.md#the-foreach-statement) statement was poorly formed.  
-  
- The following sample generates CS0230:  
-  
-```csharp  
-// CS0230.cs  
-class MyClass  
-{  
-   public static void Main()  
-   {  
-      int[] myarray = new int[3] {1,2,3};  
-  
-      foreach (int in myarray)   // CS0230  
-      {  
-         Console.WriteLine(x);  
-      }  
-   }  
-}  
-```
-
-and the sample below presents the same code, but with no CS0230 error:
-
-```csharp
-class MyClass
-{
-   public static void Main()
-   {
-      int[] myarray = new int[3] {1,2,3};
-
-      foreach (int x in myarray)  // Both type (int) and indentifier (x) are specified
-      {
-         Console.WriteLine(x);
-      }
-   }
-}
-```
diff --git a/docs/csharp/misc/cs0278.md b/docs/csharp/misc/cs0278.md
deleted file mode 100644
index 29c4433b33b33..0000000000000
--- a/docs/csharp/misc/cs0278.md
+++ /dev/null
@@ -1,34 +0,0 @@
----
-description: "Compiler Warning (level 2) CS0278"
-title: "Compiler Warning (level 2) CS0278"
-ms.date: 07/20/2015
-f1_keywords: 
-  - "CS0278"
-helpviewer_keywords: 
-  - "CS0278"
-ms.assetid: 5418cbbe-bcec-4379-a6f6-410987beb96a
----
-# Compiler Warning (level 2) CS0278
-
-'type' does not implement the 'pattern name' pattern. 'method name' is ambiguous with 'method name'.  
-  
-There are several statements in C# that rely on defined patterns, such as `foreach` and `using`. For example, the [`foreach` statement](../language-reference/statements/iteration-statements.md#the-foreach-statement) relies on the collection class implementing the "enumerable" pattern.
-  
-CS0278 can occur if the compiler is unable to make the match due to ambiguities. For example, the "enumerable" pattern requires that there be a method called `MoveNext`, and your code might contain two methods called `MoveNext`. The compiler will attempt to find an interface to use, but it is recommended that you determine and resolve the cause of the ambiguity.  
-  
-## Example  
-
- The following sample generates CS0278.  
-  
-```csharp  
-// CS0278.cs  
-using System.Collections.Generic;  
-public class myTest
-{  
-   public static void TestForeach<W>(W w)
-      where W: IEnumerable<int>, IEnumerable<string>  
-   {  
-      foreach (int i in w) {}   // CS0278  
-   }  
-}  
-```
diff --git a/docs/csharp/misc/cs0279.md b/docs/csharp/misc/cs0279.md
deleted file mode 100644
index 1219abfbd4d64..0000000000000
--- a/docs/csharp/misc/cs0279.md
+++ /dev/null
@@ -1,44 +0,0 @@
----
-description: "Compiler Warning (level 2) CS0279"
-title: "Compiler Warning (level 2) CS0279"
-ms.date: 07/20/2015
-f1_keywords: 
-  - "CS0279"
-helpviewer_keywords: 
-  - "CS0279"
-ms.assetid: 5e5faa8f-3d5b-4999-aa62-ff7f131a3e04
----
-# Compiler Warning (level 2) CS0279
-
-'type name' does not implement the 'pattern name' pattern. 'method name' is either static or not public.  
-  
- There are several statements in C# that rely on defined patterns, such as `foreach` and `using`. For example, `foreach` relies on the collection class implementing the enumerable pattern. This error occurs when the compiler is unable to make the match due to a method being declared `static` or not `public`. Methods in patterns are required to be instances of classes, and to be public.  
-  
-## Example  
-
- The following example generates CS0279:  
-  
-```csharp  
-// CS0279.cs  
-  
-using System;  
-using System.Collections;  
-  
-public class myTest : IEnumerable  
-{  
-    IEnumerator IEnumerable.GetEnumerator()  
-    {  
-        yield return 0;  
-    }  
-  
-    internal IEnumerator GetEnumerator()  
-    {  
-        yield return 0;  
-    }  
-  
-    public static void Main()  
-    {  
-        foreach (int i in new myTest()) {}  // CS0279  
-    }  
-}  
-```
diff --git a/docs/csharp/misc/cs0280.md b/docs/csharp/misc/cs0280.md
deleted file mode 100644
index 3b2cf791395b1..0000000000000
--- a/docs/csharp/misc/cs0280.md
+++ /dev/null
@@ -1,56 +0,0 @@
----
-description: "Compiler Warning (level 2) CS0280"
-title: "Compiler Warning (level 2) CS0280"
-ms.date: 07/20/2015
-f1_keywords:
-  - "CS0280"
-helpviewer_keywords:
-  - "CS0280"
-ms.assetid: 9b453478-92aa-4fd2-9b87-780fd138603a
----
-# Compiler Warning (level 2) CS0280
-
-'type' does not implement the 'pattern name' pattern. 'method name' has the wrong signature.
-
- Two statements in C#, **foreach** and **using**, rely on predefined patterns, "collection" and "resource" respectively. This warning occurs when the compiler cannot match one of these statements to its pattern due to a method's incorrect signature. For example, the "collection" pattern requires that there be a method called <xref:System.Collections.IEnumerator.MoveNext*> which takes no parameters and returns a `boolean`. Your code might contain a <xref:System.Collections.IEnumerator.MoveNext*> method that has a parameter or perhaps returns an object.
-
- The "resource" pattern and `using` provide another example. The "resource" pattern requires the <xref:System.IDisposable.Dispose*> method; if you define a property with the same name, you will get this warning.
-
- To resolve this warning, ensure that the method signatures in your type match the signatures of the corresponding methods in the pattern, and ensure that you have no properties with the same name as a method required by the pattern.
-
-## Example
-
- The following sample generates CS0280.
-
-```csharp
-// CS0280.cs
-using System;
-using System.Collections;
-
-public class ValidBase: IEnumerable
-{
-   IEnumerator IEnumerable.GetEnumerator()
-   {
-      yield return 0;
-   }
-
-   internal IEnumerator GetEnumerator()
-   {
-      yield return 0;
-   }
-}
-
-class Derived : ValidBase
-{
-   // field, not method
-   new public int GetEnumerator;
-}
-
-public class Test
-{
-   public static void Main()
-   {
-      foreach (int i in new Derived()) {}   // CS0280
-   }
-}
-```
diff --git a/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md b/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md
index 9c6218dedcd3b..4ea353a2ab2cd 100644
--- a/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md
+++ b/docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md
@@ -178,7 +178,6 @@ f1_keywords:
   - "CS8183"
   - "CS8184"
   - "CS8185"
-  - "CS8186"
   - "CS8187"
   - "CS8188"
   - "CS8189"
@@ -225,21 +224,10 @@ f1_keywords:
   - "CS8383"
   - "CS8384"
   # C# 8.0 diagnostics
-  ## Async enumerables
-  - "CS8412"
-  - "CS8413"
-  - "CS8414"
-  - "CS8415"
-  - "CS8419"
-  - "CS8420"
   ## Static local functions
   - "CS8421"
   ## Attributes
   - "CS8423"
-  ## More async enumerators
-  - "CS8424"
-  - "CS8425"
-  - "CS8426"
   ## Index and range
   - "CS8428"
   - "CS8429"
@@ -262,7 +250,6 @@ f1_keywords:
   - "CS9349"
   - "CS9350"
   - "CS9351"
-  - "CS9353"
 # Collection arguments:
   - "CS9354"
   - "CS9355"