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System.AttributeUsageAttribute F# snippets (#7526)
* System.AttributeUsageAttribute F# snippets * Update AttributeUsageAttribute.xml
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‎samples/snippets/fsharp/VS_Snippets_CLR_Classic/classic AttributeUsageAttribute.AttributeUsageAttribute Example/FS/fs.fsproj‎

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

‎samples/snippets/fsharp/VS_Snippets_CLR_Classic/classic AttributeUsageAttribute.AttributeUsageAttribute Example/FS/source.fs‎

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// <Snippet1>
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namespace System.Runtime.InteropServices
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open System
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[<AttributeUsage(AttributeTargets.Method ||| AttributeTargets.Field ||| AttributeTargets.Property)>]
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type DispIdAttribute(value: int) =
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inherit Attribute()
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// . . .
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member _.Value with get() =
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// . . .
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0
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// </Snippet1>

‎samples/snippets/fsharp/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/fs/Inherited1.fs‎

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open System
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// <Snippet1>
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[<AttributeUsage(AttributeTargets.Class ||| AttributeTargets.Method ||| AttributeTargets.Property ||| AttributeTargets.Field, Inherited = true)>]
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type InheritedAttribute() =
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inherit Attribute()
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[<AttributeUsage(AttributeTargets.Class ||| AttributeTargets.Method ||| AttributeTargets.Property ||| AttributeTargets.Field, Inherited = false)>]
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type NotInheritedAttribute() =
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inherit Attribute()
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// </Snippet1>
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// <Snippet2>
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[<Inherited>]
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type BaseA() =
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abstract member MethodA: unit -> unit
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[<Inherited>]
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default _.MethodA() = ()
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type DerivedA() =
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inherit BaseA()
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override _.MethodA() = ()
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[<NotInherited>]
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type BaseB() =
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abstract member MethodB: unit -> unit
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[<NotInherited>]
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default _.MethodB() = ()
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type DerivedB() =
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inherit BaseB()
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override _.MethodB() = ()
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let typeA = typeof<DerivedA>
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printfn $"DerivedA has Inherited attribute: {typeA.GetCustomAttributes(typeof<InheritedAttribute>, true).Length > 0}"
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let memberA = typeA.GetMethod "MethodA"
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printfn $"DerivedA.MemberA has Inherited attribute: {memberA.GetCustomAttributes(typeof<InheritedAttribute>, true).Length > 0}\n"
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let typeB = typeof<DerivedB>
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printfn $"DerivedB has NotInherited attribute: {typeB.GetCustomAttributes(typeof<NotInheritedAttribute>, true).Length > 0}"
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let memberB = typeB.GetMethod "MethodB"
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printfn $"DerivedB.MemberB has NotInherited attribute: {memberB.GetCustomAttributes(typeof<NotInheritedAttribute>, true).Length > 0}"
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// The example displays the following output:
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// DerivedA has Inherited attribute: True
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// DerivedA.MemberA has Inherited attribute: True
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//
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// DerivedB has NotInherited attribute: False
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// DerivedB.MemberB has NotInherited attribute: False
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// </Snippet2>

‎samples/snippets/fsharp/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/fs/fs.fsproj‎

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<Project Sdk="Microsoft.NET.Sdk">
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<PropertyGroup>
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<OutputType>Exe</OutputType>
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<TargetFramework>net6.0</TargetFramework>
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</PropertyGroup>
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<ItemGroup>
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<Compile Include="Inherited1.fs" />
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</ItemGroup>
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</Project>

‎xml/System/AttributeUsageAttribute.xml‎

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:::code language="cpp" source="~/samples/snippets/cpp/VS_Snippets_CLR_Classic/classic AttributeUsageAttribute.AttributeUsageAttribute Example/CPP/source.cpp" id="Snippet1":::
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:::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_Classic/classic AttributeUsageAttribute.AttributeUsageAttribute Example/CS/source.cs" id="Snippet1":::
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:::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_Classic/classic AttributeUsageAttribute.AttributeUsageAttribute Example/FS/source.fs" id="Snippet1":::
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:::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_Classic/classic AttributeUsageAttribute.AttributeUsageAttribute Example/VB/source.vb" id="Snippet1":::
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]]></format>
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The following example illustrates the difference between an attribute to which an <xref:System.AttributeUsageAttribute> attribute with an <xref:System.AttributeUsageAttribute.Inherited%2A> property value of `true` is applied and one to which <xref:System.AttributeUsageAttribute> attribute with an <xref:System.AttributeUsageAttribute.Inherited%2A> property value of `false` is applied. The example defines two attributes, `InheritedAttribute` and `NotInheritedAttribute`. Both attributes can apply to classes and methods. Because the <xref:System.AttributeUsageAttribute.Inherited%2A> property of the <xref:System.AttributeUsageAttribute> attribute applied to `InheritedAttribute` is `true`, it is inherited by derived classes and the members of derived classes that override the base class method. On the other hand, because the <xref:System.AttributeUsageAttribute.Inherited%2A> property of the <xref:System.AttributeUsageAttribute> attribute applied to `NotInheritedAttribute` is `false`, it is not inherited by derived classes and the members of derived classes that override the base class method.
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:::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/cs/Inherited1.cs" id="Snippet1":::
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:::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/fs/Inherited1.fs" id="Snippet1":::
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:::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/vb/Inherited1.vb" id="Snippet1":::
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The example then defines two base classes. The first, `BaseA`, has a single method, `MethodA`. The second, `BaseB`, has a single method, `MethodB`. `BaseA` and `MethodA` are tagged with the `InheritedAttribute` attribute, and `BaseB` and `MethodB` are tagged with the `NotInheritedAttribute` attribute. `DerivedA` inherits from `BaseA` and overrides its `MethodA` method. `DerivedB` inherits from `BaseB` and overrides its `MethodB` method.
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:::code language="csharp" source="~/samples/snippets/csharp/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/cs/Inherited1.cs" id="Snippet2":::
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:::code language="fsharp" source="~/samples/snippets/fsharp/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/fs/Inherited1.fs" id="Snippet2":::
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:::code language="vb" source="~/samples/snippets/visualbasic/VS_Snippets_CLR_System/System.AttributeUsageAttribute.Inherited/vb/Inherited1.vb" id="Snippet2":::
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As the output from the example shows, `DerivedA` and `DerivedA.MethodA` inherit the `InheritedAttribute` attribute, but `DerivedB` and `DerivedB.MethodB` do not inherit the `NotInheritedAttribute` attribute.

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