Add System.Action<T> F# snippets (#7380)

* Add System.Action<T> F# snippets

* Update Lambda.fs

* Update action.fs

Author: albert-du

samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action_PrintExample/fs/action.fs

@@ -0,0 +1,30 @@
+open System
+
+//<snippet01>
+// F# provides a type alias for System.Collections.List<'T> as ResizeArray<'T>.
+let names = ResizeArray<string>()
+names.Add "Bruce"
+names.Add "Alfred"
+names.Add "Tim"
+names.Add "Richard"
+
+let print s = printfn "%s" s
+
+// Display the contents of the list using the print function.
+names.ForEach(Action<string> print)
+
+// The following demonstrates the lambda expression feature of F#
+// to display the contents of the list to the console.
+names.ForEach(fun s -> printfn "%s" s)
+
+(* This code will produce output similar to the following:
+* Bruce
+* Alfred
+* Tim
+* Richard
+* Bruce
+* Alfred
+* Tim
+* Richard
+*)
+//</snippet01>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action_PrintExample/fs/action.fsproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="action.fs" />
+  </ItemGroup>
+
+</Project>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action~1/fs/Action1.fs

@@ -0,0 +1,20 @@
+module TestAction1
+
+// <Snippet2>
+open System
+open System.Windows.Forms
+
+let showWindowsMessage message = 
+    MessageBox.Show message |> ignore
+
+let messageTarget =
+    Action<string>(
+        if Environment.GetCommandLineArgs().Length > 1 then
+            showWindowsMessage
+        else
+            printfn "%s"
+    )
+
+messageTarget.Invoke "Hello, World!"
+
+// </Snippet2>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action~1/fs/Action1.fsproj

@@ -0,0 +1,16 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0-windows</TargetFramework>
+    <DisableWinExeOutputInference>true</DisableWinExeOutputInference>
+    <UseWindowsForms>true</UseWindowsForms>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Action1.fs" />
+    <Compile Include="Delegate.fs" />
+    <Compile Include="Lambda.fs" />
+  </ItemGroup>
+
+</Project>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action~1/fs/Delegate.fs

@@ -0,0 +1,22 @@
+module TestCustomDelegate
+
+// <Snippet1>
+open System
+open System.Windows.Forms
+
+type DisplayMessage = delegate of message: string -> unit
+
+let showWindowsMessage message = 
+    MessageBox.Show message |> ignore
+
+let messageTarget =
+    DisplayMessage(
+        if Environment.GetCommandLineArgs().Length > 1 then
+            showWindowsMessage
+        else
+            printfn "%s"
+    )
+
+messageTarget.Invoke "Hello, World!"
+
+// </Snippet1>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action~1/fs/Lambda.fs

@@ -0,0 +1,20 @@
+module TestLambdaExpression
+
+// <Snippet4>
+open System
+open System.Windows.Forms
+
+let showWindowsMessage message = 
+    MessageBox.Show message |> ignore
+
+let messageTarget =
+    Action<string>(
+        if Environment.GetCommandLineArgs().Length > 1 then
+            fun s -> showWindowsMessage s
+        else
+            fun s -> printfn "%s" s
+    )
+
+messageTarget.Invoke "Hello, World!"
+
+// </Snippet4>

xml/System/Action`1.xml

@@ -69,12 +69,14 @@
   
  :::code language="cpp" source="~/samples/snippets/cpp/VS_Snippets_CLR_System/system.Action~1/cpp/delegate.cpp" id="Snippet1":::
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_System/system.Action~1/cs/Delegate.cs" id="Snippet1":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action~1/fs/Delegate.fs" id="Snippet1":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_System/system.Action~1/vb/Delegate.vb" id="Snippet1":::  
   
  The following example simplifies this code by instantiating the <xref:System.Action%601> delegate instead of explicitly defining a new delegate and assigning a named method to it.  
   
  :::code language="cpp" source="~/samples/snippets/cpp/VS_Snippets_CLR_System/system.Action~1/cpp/action`1.cpp" id="Snippet2":::
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_System/system.Action~1/cs/Action1.cs" id="Snippet2":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action~1/fs/Action1.fs" id="Snippet2":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_System/system.Action~1/vb/Action1.vb" id="Snippet2":::  
   
  You can also use the <xref:System.Action%601> delegate with anonymous methods in C#, as the following example illustrates. (For an introduction to anonymous methods, see [Anonymous Methods](/dotnet/csharp/programming-guide/statements-expressions-operators/anonymous-methods).)  
@@ -84,6 +86,7 @@
  You can also assign a lambda expression to an <xref:System.Action%601> delegate instance, as the following example illustrates. (For an introduction to lambda expressions, see [Lambda Expressions](/dotnet/csharp/programming-guide/statements-expressions-operators/lambda-expressions).)  
   
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_System/system.Action~1/cs/Lambda.cs" id="Snippet4":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action~1/fs/Lambda.fs" id="Snippet4":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_System/system.Action~1/vb/lambda.vb" id="Snippet4":::  
   
  The <xref:System.Collections.Generic.List%601.ForEach%2A> and <xref:System.Array.ForEach%2A> methods each take an <xref:System.Action%601> delegate as a parameter. The method encapsulated by the delegate allows you to perform an action on each element in the array or list. The example uses the <xref:System.Collections.Generic.List%601.ForEach%2A> method to provide an illustration.  
@@ -94,6 +97,7 @@
  The following example demonstrates the use of the <xref:System.Action%601> delegate to print the contents of a <xref:System.Collections.Generic.List%601> object. In this example, the `Print` method is used to display the contents of the list to the console. In addition, the C# example also demonstrates the use of anonymous methods to display the contents to the console. Note that the example does not explicitly declare an <xref:System.Action%601> variable. Instead, it passes a reference to a method that takes a single parameter and that does not return a value to the <xref:System.Collections.Generic.List%601.ForEach%2A?displayProperty=nameWithType> method, whose single parameter is an <xref:System.Action%601> delegate. Similarly, in the C# example, an <xref:System.Action%601> delegate is not explicitly instantiated because the signature of the anonymous method matches the signature of the <xref:System.Action%601> delegate that is expected by the <xref:System.Collections.Generic.List%601.ForEach%2A?displayProperty=nameWithType> method.  
 
  :::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_System/system.Action_PrintExample/cs/action.cs" interactive="try-dotnet-method" id="Snippet01":::
+ :::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_System/system.Action_PrintExample/fs/action.fs" id="Snippet01":::
  :::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_System/system.Action_PrintExample/vb/action.vb" id="Snippet01":::  
   
  ]]></format>