Replace extension method with member

Where samples use `this` extension methods, except where explaining the `this` syntax, convert to the C# 14 extension member syntax,

Author: BillWagner

docs/csharp/language-reference/attributes/caller-information.md

@@ -58,7 +58,7 @@ The compiler injects the expression used for `condition` into the `message` argu
 Argument failed validation: <func is not null>
 ```
 
-This attribute enables you to write diagnostic utilities that provide more details. Developers can more quickly understand what changes are needed. You can also use the <xref:System.Runtime.CompilerServices.CallerArgumentExpressionAttribute> to determine what expression was used as the receiver for extension methods. The following method samples a sequence at regular intervals. If the sequence has fewer elements than the frequency, it reports an error:
+This attribute enables you to write diagnostic utilities that provide more details. Developers can more quickly understand what changes are needed. You can also use the <xref:System.Runtime.CompilerServices.CallerArgumentExpressionAttribute> to determine what expression was used as the receiver for extension members. The following method samples a sequence at regular intervals. If the sequence has fewer elements than the frequency, it reports an error:
 
 :::code language="csharp" source="./snippets/CallerInformation.cs" id="ExtensionMethod":::
 

docs/csharp/language-reference/attributes/snippets/CallerInformation.cs

@@ -56,16 +56,19 @@ public static void ValidateArgument(string parameterName, bool condition, [Calle
 public static class Extensions
 {
     // <ExtensionMethod>
-    public static IEnumerable<T> Sample<T>(this IEnumerable<T> sequence, int frequency, 
-        [CallerArgumentExpression(nameof(sequence))] string? message = null)
+    extension(IEnumerable<T> sequence)
     {
-        if (sequence.Count() < frequency)
-            throw new ArgumentException($"Expression doesn't have enough elements: {message}", nameof(sequence));
-        int i = 0;
-        foreach (T item in sequence)
+        public static IEnumerable<T> Sample<T>(int frequency, 
+            [CallerArgumentExpression(nameof(sequence))] string? message = null)
         {
-            if (i++ % frequency == 0)
-                yield return item;
+            if (sequence.Count() < frequency)
+                throw new ArgumentException($"Expression doesn't have enough elements: {message}", nameof(sequence));
+            int i = 0;
+            foreach (T item in sequence)
+            {
+                if (i++ % frequency == 0)
+                    yield return item;
+            }
         }
     }
     // </ExtensionMethod>

docs/csharp/language-reference/attributes/snippets/attributes.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net9.0</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <Nullable>enable</Nullable>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <ImplicitUsings>enable</ImplicitUsings>

docs/csharp/language-reference/builtin-types/built-in-types.md

@@ -1,7 +1,7 @@
 ---
 title: "Built-in types"
 description: "Learn C# built-in value and reference types"
-ms.date: 03/07/2025
+ms.date: 11/24/2025
 helpviewer_keywords:
   - "types [C#], built-in"
   - "built-in C# types"
@@ -62,7 +62,7 @@ The C# language includes specialized rules for the <xref:System.Span`1?displayPr
 - From `System.ReadOnlySpan<E>` to `System.ReadOnlySpan<U>`, when `E` has a covariance conversion or an identity conversion to `U`
 - From `string` to `System.ReadOnlySpan<char>`
 
-The compiler never ignores any user defined conversion where an applicable *implicit span conversion* exists. Implicit span conversions can be applied to the first argument of [extension methods](../../programming-guide/classes-and-structs/extension-methods.md), the parameter with the `this` modifier. Implicit span conversions aren't considered for method group conversions.
+The compiler never ignores any user defined conversion where an applicable *implicit span conversion* exists. Implicit span conversions can be applied to the first argument of [extension members](../../programming-guide/classes-and-structs/extension-methods.md), the parameter with the `this` modifier. Implicit span conversions aren't considered for method group conversions.
 
 ## See also
 

docs/csharp/language-reference/builtin-types/enum.md

@@ -1,7 +1,7 @@
 ---
 title: "Enumeration types"
 description: "Learn about C# enumeration types that represent a choice or a combination of choices"
-ms.date: 12/13/2019
+ms.date: 11/24/2025
 f1_keywords:
   - "enum"
   - "enum_CSharpKeyword"
@@ -10,7 +10,6 @@ helpviewer_keywords:
   - "enum type [C#]"
   - "enumeration type [C#]"
   - "bit flags [C#]"
-ms.assetid: bbeb9a0f-e9b3-41ab-b0a6-c41b1a08974c
 ---
 # Enumeration types (C# reference)
 
@@ -38,7 +37,7 @@ enum ErrorCode : ushort
 }
 ```
 
-You cannot define a method inside the definition of an enumeration type. To add functionality to an enumeration type, create an [extension method](../../programming-guide/classes-and-structs/extension-methods.md).
+You can't define a method inside the definition of an enumeration type. To add functionality to an enumeration type, create an [extension member](../../programming-guide/classes-and-structs/extension-methods.md).
 
 The default value of an enumeration type `E` is the value produced by expression `(E)0`, even if zero doesn't have the corresponding enum member.
 
@@ -48,9 +47,9 @@ C# allows implicit conversions from the literal value `0` to any enum type, and
 
 :::code language="csharp" source="snippets/shared/EnumType.cs" id="SnippetZeroConversions":::
 
-In the preceding example, both `port1` and `port2` are assigned the value `0`, but `GpioPort` has no member with that value. The <xref:System.Enum.IsDefined%2A?displayProperty=nameWithType> method confirms these are invalid enum values.
+In the preceding example, both `port1` and `port2` are assigned to the value `0`, but `GpioPort` has no member with that value. The <xref:System.Enum.IsDefined%2A?displayProperty=nameWithType> method confirms that 0 is an invalid enum value.
 
-This implicit conversion exists because the 0 bit pattern is the default for all struct types, including all enum types. However, it can introduce bugs in your code. To avoid these issues:
+This implicit conversion exists because the 0-bit pattern is the default for all struct types, including all enum types. However, it can introduce bugs in your code. To avoid these issues:
 
 - You should almost always define a member with value `0` in your enums.
 - Use <xref:System.Enum.IsDefined%2A?displayProperty=nameWithType> to validate enum values when converting from numeric types.
@@ -62,21 +61,21 @@ You use an enumeration type to represent a choice from a set of mutually exclusi
 
 If you want an enumeration type to represent a combination of choices, define enum members for those choices such that an individual choice is a bit field. That is, the associated values of those enum members should be the powers of two. Then, you can use the [bitwise logical operators `|` or `&`](../operators/bitwise-and-shift-operators.md#enumeration-logical-operators) to combine choices or intersect combinations of choices, respectively. To indicate that an enumeration type declares bit fields, apply the [Flags](xref:System.FlagsAttribute) attribute to it. As the following example shows, you can also include some typical combinations in the definition of an enumeration type.
 
-[!code-csharp[enum flags](snippets/shared/EnumType.cs#Flags)]
+:::code language="csharp" source="snippets/shared/EnumType.cs" id="SnippetFlags":::
 
 For more information and examples, see the <xref:System.FlagsAttribute?displayProperty=nameWithType> API reference page and the [Non-exclusive members and the Flags attribute](../../../fundamentals/runtime-libraries/system-enum.md#non-exclusive-members-and-the-flags-attribute) section of the <xref:System.Enum?displayProperty=nameWithType> API reference page.
 
 ## The System.Enum type and enum constraint
 
-The <xref:System.Enum?displayProperty=nameWithType> type is the abstract base class of all enumeration types. It provides a number of methods to get information about an enumeration type and its values. For more information and examples, see the <xref:System.Enum?displayProperty=nameWithType> API reference page.
+The <xref:System.Enum?displayProperty=nameWithType> type is the abstract base class of all enumeration types. It provides many methods to get information about an enumeration type and its values. For more information and examples, see the <xref:System.Enum?displayProperty=nameWithType> API reference page.
 
 You can use `System.Enum` in a base class constraint (that is known as the [enum constraint](../../programming-guide/generics/constraints-on-type-parameters.md#enum-constraints)) to specify that a type parameter is an enumeration type. Any enumeration type also satisfies the `struct` constraint, which is used to specify that a type parameter is a non-nullable value type.
 
 ## Conversions
 
 For any enumeration type, there exist explicit conversions between the enumeration type and its underlying integral type. If you [cast](../operators/type-testing-and-cast.md#cast-expression) an enum value to its underlying type, the result is the associated integral value of an enum member.
 
-[!code-csharp[enum conversions](snippets/shared/EnumType.cs#Conversions)]
+:::code language="csharp" source="snippets/shared/EnumType.cs" id="SnippetConversions":::
 
 Use the <xref:System.Enum.IsDefined%2A?displayProperty=nameWithType> method to determine whether an enumeration type contains an enum member with the certain associated value.
 

docs/csharp/language-reference/compiler-messages/cs0122.md

@@ -14,7 +14,7 @@ ms.assetid: 5f639a66-c807-4166-b88a-93e5f272ceb7
 
  The [access modifier](../keywords/index.md) for a class member prevents accessing the member. For more information, see [Access Modifiers](../../programming-guide/classes-and-structs/access-modifiers.md).
 
- [Extension methods](../../programming-guide/classes-and-structs/extension-methods.md) cannot access private members of the type they are extending.
+ [Extension members](../../programming-guide/classes-and-structs/extension-methods.md) cannot access private members of the type they are extending.
 
  One cause of this (not shown in the sample below) can be omitting the **/out** compiler flag on the target of a friend assembly. For more information, see [Friend Assemblies](../../../standard/assembly/friend.md) and [**OutputAssembly** (C# Compiler Options)](../compiler-options/output.md#outputassembly).
 

docs/csharp/language-reference/keywords/method-parameters.md

@@ -80,7 +80,7 @@ You can't use the previous parameter modifiers in the following kinds of methods
 - Async methods, which you define by using the [async](async.md) modifier.
 - Iterator methods, which include a [yield return](../statements/yield.md) or `yield break` statement.
 
-[Extension methods](../../programming-guide/classes-and-structs/extension-methods.md) also have restrictions on the use of these argument keywords:
+[Extension members](../../programming-guide/classes-and-structs/extension-methods.md) also have restrictions on the use of these argument keywords:
 
 - The `out` keyword can't be used on the first argument of an extension method.
 - The `ref` keyword can't be used on the first argument of an extension method when the argument isn't a `struct`, or a generic type not constrained to be a struct.

docs/csharp/language-reference/keywords/snippets/GenericWhereConstraints.cs

@@ -3,8 +3,6 @@
 using System.Collections.Generic;
 using System.Text;
 
-using static Keywords.UnmanagedExtensions;
-
 namespace Keywords
 {
     // <Snippet1>
@@ -84,213 +82,11 @@ public void MyMethod<T>(T t) where T : IMyInterface { }
         // </Snippet8>
     }
 
-    // <Snippet9>
-    public class Employee
-    {
-        public Employee(string s, int i) => (Name, ID) = (s, i);
-        public string Name { get; set; }
-        public int ID { get; set; }
-    }
-
-    public class GenericList<T> where T : Employee
-    {
-        private class Node
-        {
-            public Node(T t) => (Next, Data) = (null, t);
-
-            public Node Next { get; set; }
-            public T Data { get; set; }
-        }
-
-        private Node head;
-
-        public void AddHead(T t)
-        {
-            Node n = new Node(t) { Next = head };
-            head = n;
-        }
-
-        public IEnumerator<T> GetEnumerator()
-        {
-            Node current = head;
-
-            while (current != null)
-            {
-                yield return current.Data;
-                current = current.Next;
-            }
-        }
-
-        public T FindFirstOccurrence(string s)
-        {
-            Node current = head;
-            T t = null;
-
-            while (current != null)
-            {
-                //The constraint enables access to the Name property.
-                if (current.Data.Name == s)
-                {
-                    t = current.Data;
-                    break;
-                }
-                else
-                {
-                    current = current.Next;
-                }
-            }
-            return t;
-        }
-    }
-    // </Snippet9>
 
     public interface IEmployee
     {
     }
 
-    // <Snippet10>
-    class EmployeeList<T> where T : Employee, IEmployee, System.IComparable<T>, new()
-    {
-        // ...
-    }
-    // </Snippet10>
-
-    // <Snippet12>
-    class Base { }
-    class Test<T, U>
-        where U : struct
-        where T : Base, new()
-    { }
-    // </Snippet12>
-
-    namespace ListExample
-    {
-        // <Snippet13>
-        public class List<T>
-        {
-            public void Add<U>(List<U> items) where U : T {/*...*/}
-        }
-        // </Snippet13>
-    }
-
-    // <Snippet14>
-    //Type parameter V is used as a type constraint.
-    public class SampleClass<T, U, V> where T : V { }
-    // </Snippet14>
-
-    public static class UnmanagedExtensions
-    {
-        // <Snippet15>
-        unsafe public static byte[] ToByteArray<T>(this T argument) where T : unmanaged
-        {
-            var size = sizeof(T);
-            var result = new Byte[size];
-            Byte* p = (byte*)&argument;
-            for (var i = 0; i < size; i++)
-                result[i] = *p++;
-            return result;
-        }
-        // </Snippet15>
-
-        // <Snippet16>
-        public static TDelegate TypeSafeCombine<TDelegate>(this TDelegate source, TDelegate target)
-            where TDelegate : System.Delegate
-            => Delegate.Combine(source, target) as TDelegate;
-        // </Snippet16>
-
-        // <Snippet18>
-        public static Dictionary<int, string> EnumNamedValues<T>() where T : System.Enum
-        {
-            var result = new Dictionary<int, string>();
-            var values = Enum.GetValues(typeof(T));
-
-            foreach (int item in values)
-                result.Add(item, Enum.GetName(typeof(T), item));
-            return result;
-        }
-        // </Snippet18>
-    }
-    public static class GenericWhereConstraints
-    {
-        public static void Examples()
-        {
-            TestStringEquality();
-            TestUnmanaged();
-            TestDelegateCombination();
-            TestEnumValues();
-        }
-
-        // <Snippet11>
-        public static void OpEqualsTest<T>(T s, T t) where T : class
-        {
-            System.Console.WriteLine(s == t);
-        }
-        private static void TestStringEquality()
-        {
-            string s1 = "target";
-            System.Text.StringBuilder sb = new System.Text.StringBuilder("target");
-            string s2 = sb.ToString();
-            OpEqualsTest<string>(s1, s2);
-        }
-        // </Snippet11>
-
-        public struct Point3D
-        {
-            public double X { get; set; }
-            public double Y { get; set; }
-            public double Z { get; set; }
-        }
-        private static void TestUnmanaged()
-        {
-            var thing = new Point3D { X = 1, Y = 2, Z = 3 };
-
-            var storage = thing.ToByteArray();
-
-            for (int i = 0; i < storage.Length; i++)
-                Console.Write($"{storage[i]:X2}, ");
-            Console.WriteLine();
-        }
-
-        private static void TestDelegateCombination()
-        {
-            // <Snippet17>
-            Action first = () => Console.WriteLine("this");
-            Action second = () => Console.WriteLine("that");
-
-            var combined = first.TypeSafeCombine(second);
-            combined();
-
-            Func<bool> test = () => true;
-            // Combine signature ensures combined delegates must
-            // have the same type.
-            //var badCombined = first.TypeSafeCombine(test);
-            // </Snippet17>
-        }
-
-        // <Snippet19>
-        enum Rainbow
-        {
-            Red,
-            Orange,
-            Yellow,
-            Green,
-            Blue,
-            Indigo,
-            Violet
-        }
-        // </Snippet19>
-        private static void TestEnumValues()
-        {
-            // <Snippet20>
-            var map = EnumNamedValues<Rainbow>();
-
-            foreach (var pair in map)
-                Console.WriteLine($"{pair.Key}:\t{pair.Value}");
-
-            // </Snippet20>
-        }
-    }
-
     // <BaseClass>
     public abstract class B
     {

docs/csharp/language-reference/keywords/snippets/Program.cs

@@ -8,8 +8,6 @@ class Program
     {
         static async Task Main(string[] args)
         {
-            Console.WriteLine("=================    Generic Where Constraints Examples ======================");
-            GenericWhereConstraints.Examples();
             Console.WriteLine("=================    readonly Keyword Examples ======================");
             ReadonlyKeywordExamples.Examples();
             Console.WriteLine("=================    pass by value / reference Keyword Examples ======================");

docs/csharp/language-reference/keywords/this.md

@@ -13,7 +13,7 @@ helpviewer_keywords:
 The `this` keyword refers to the current instance of the class and is also used as a modifier of the first parameter of an extension method.
 
 > [!NOTE]
-> This article discusses the use of `this` with class instances. For more information about its use in extension methods, see the [`extension`](./extension.md) keyword.
+> This article discusses the use of `this` to refer to the receiver instance in the current member. For more information about its use in extension methods, see the [`extension`](./extension.md) keyword.
 
 The following are common uses of `this`: