System.Activator F# snippets (dotnet#7421)

* System.Activator F# snippets

* Update createinstanceex1a.fs

* update snippets

Author: albert-du

samples/snippets/fsharp/VS_Snippets_CLR/ActivatorX/fs/ActivatorX.fs

@@ -0,0 +1,37 @@
+module ActivatorX
+
+//<snippet1>
+open System
+open System.Reflection
+open System.Text
+
+type SomeType() =
+    member _.DoSomething(x) = printfn $"100 / {x} = {100 / x}"
+
+//<snippet2>
+// Create an instance of the StringBuilder type using Activator.CreateInstance.
+let o = Activator.CreateInstance typeof<StringBuilder>
+
+// Append a string into the StringBuilder object and display the StringBuilder.
+let sb = o :?> StringBuilder
+sb.Append "Hello, there." |> ignore
+printfn $"{sb}"
+//</snippet2>
+
+//<snippet3>
+// Create an instance of the SomeType class that is defined in this assembly.
+let oh = 
+    Activator.CreateInstanceFrom(Assembly.GetEntryAssembly().Location, typeof<SomeType>.FullName)
+
+// Call an instance method defined by the SomeType type using this object.
+let st = oh.Unwrap() :?> SomeType
+
+st.DoSomething 5
+//</snippet3>
+
+(* This code produces the following output:
+
+Hello, there.
+100 / 5 = 20
+ *)
+//</snippet1>

samples/snippets/fsharp/VS_Snippets_CLR/ActivatorX/fs/ActivatorX.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="ActivatorX.fs" />
+    <Compile Include="source2.fs" />
+  </ItemGroup>
+
+</Project>

samples/snippets/fsharp/VS_Snippets_CLR/ActivatorX/fs/source2.fs

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+module source2
+
+//<snippet4>
+open System
+
+let instanceSpec =
+    "System.EventArgs;System.Random;System.Exception;System.Object;System.Version"
+
+let instances = instanceSpec.Split ';'
+let instlist = Array.zeroCreate instances.Length
+let mutable item = obj ()
+
+for i = 0 to instances.Length - 1 do
+    // create the object from the specification string
+    printfn $"Creating instance of: {instances.[i]}"
+    item <- Activator.CreateInstance(Type.GetType instances.[i])
+    instlist.[i] <- item
+
+printfn "\nObjects and their default values:\n"
+
+for o in instlist do
+    printfn $"Type:     {o.GetType().FullName}\nValue:    {o}\nHashCode: {o.GetHashCode()}\n"
+
+
+// This program will display output similar to the following:
+//
+// Creating instance of: System.EventArgs
+// Creating instance of: System.Random
+// Creating instance of: System.Exception
+// Creating instance of: System.Object
+// Creating instance of: System.Version
+//
+// Objects and their default values:
+//
+// Type:     System.EventArgs
+// Value:    System.EventArgs
+// HashCode: 46104728
+//
+// Type:     System.Random
+// Value:    System.Random
+// HashCode: 12289376
+//
+// Type:     System.Exception
+// Value:    System.Exception: Exception of type 'System.Exception' was thrown.
+// HashCode: 55530882
+//
+// Type:     System.Object
+// Value:    System.Object
+// HashCode: 30015890
+//
+// Type:     System.Version
+// Value:    0.0
+// HashCode: 1048575
+//</snippet4>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.activation.createinstance~~1/fs/remarks.fs

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+module remarks
+
+// <Snippet1>
+let factory<'T when 'T : (new: unit -> 'T)> =
+    new 'T()
+// </Snippet1>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.activation.createinstance~~1/fs/remarks.fsproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="remarks.fs" />
+  </ItemGroup>
+
+</Project>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.activator.createinstance/fs/CreateInstance5.fs

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+module CreateInstance5
+// <Snippet5>
+open System
+
+// Initialize array of characters from a to z.
+let chars = [| 'a' .. 'z' |]
+
+let obj = Activator.CreateInstance(typeof<string>, chars[13..22])
+
+printfn $"{obj}"
+
+// The example displays the following output:
+//       nopqrstuvw
+// </Snippet5>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.activator.createinstance/fs/PersonInfo/PersonInfo.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="..\personinfo.fs" />
+  </ItemGroup>
+
+</Project>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.activator.createinstance/fs/createinstance.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="createinstanceex1.fs" />
+    <Compile Include="createinstanceex1a.fs" />
+    <Compile Include="createinstance2.fs" />
+    <Compile Include="CreateInstance5.fs" />
+  </ItemGroup>
+  
+  <ItemGroup>
+    <ProjectReference Include="PersonInfo\PersonInfo.fsproj"/>
+  </ItemGroup>
+
+
+</Project>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.activator.createinstance/fs/createinstance2.fs

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+module createinstanceex2
+// <Snippet4>
+open System
+
+let chars = [| 'a' .. 'f' |]
+
+let arguments =
+    [| chars
+       chars[1..4]
+       Array.create 20 chars[1] |]
+
+for args in arguments do
+    let result =
+        Activator.CreateInstance(typeof<string>, args)
+
+    printfn $"{result.GetType().Name}: {result}"
+
+// The example displays the following output:
+//    String: abcdef
+//    String: bcde
+//    String: bbbbbbbbbbbbbbbbbbbb
+// </Snippet4>

samples/snippets/fsharp/VS_Snippets_CLR_System/system.activator.createinstance/fs/createinstanceex1.fs

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+module createinstanceex1
+
+// <Snippet2>
+open System
+
+let handle = Activator.CreateInstance("PersonInfo", "Person")
+let p = handle.Unwrap() :?> Person
+p.Name <- "Samuel"
+printfn $"{p}"
+
+// The example displays the following output:
+//        Samuel
+// </Snippet2>