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ValueType F# snippets (#8073)
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‎snippets/fsharp/System/ValueType/Equals/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>

‎snippets/fsharp/System/ValueType/Equals/source.fs‎

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//<snippet1>
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type Complex() =
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member val m_Re = 0. with get, set
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member val m_Im = 0. with get, set
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override this.Equals(ob) =
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match ob with
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| :? Complex as c ->
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this.m_Re = c.m_Re && this.m_Im = c.m_Im
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| _ -> false
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override this.GetHashCode() =
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this.m_Re.GetHashCode() ^^^ this.m_Im.GetHashCode()
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//</snippet1>

‎snippets/fsharp/System/ValueType/Overview/example1.fs‎

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// <Snippet1>
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open System
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open System.Numerics
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module Utility =
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type NumericRelationship =
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| GreaterThan = 1
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| EqualTo = 0
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| LessThan = -1
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let isInteger (value: ValueType) =
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match value with
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| :? sbyte | :? int16 | :? int32 | :? int64
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| :? byte | :? uint16 | :? uint32
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| :? uint64 | :? bigint -> true
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| _ -> false
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let isFloat (value: ValueType) =
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match value with
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| :? float32 | :? float | :? decimal -> true
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| _ -> false
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let tryToBigInt (value: ValueType) =
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match value with
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| :? sbyte as v -> bigint v |> Some
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| :? int16 as v -> bigint v |> Some
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| :? int32 as v -> bigint v |> Some
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| :? int64 as v -> bigint v |> Some
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| :? byte as v -> bigint v |> Some
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| :? uint16 as v -> bigint v |> Some
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| :? uint32 as v -> bigint v |> Some
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| :? uint64 as v -> bigint v |> Some
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| :? float32 as v -> bigint v |> Some
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| _ -> None
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let isNumeric (value: ValueType) =
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isInteger value || isFloat value
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let compare (value1: ValueType) (value2: ValueType) =
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if isNumeric value1 |> not then
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invalidArg "value1" "value1 is not a number."
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elif isNumeric value2 |> not then
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invalidArg "value2" "value2 is not a number."
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// Use BigInteger as common integral type
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match tryToBigInt value1, tryToBigInt value2 with
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| Some bigint1, Some bigint2 ->
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BigInteger.Compare(bigint1, bigint2) |> enum<NumericRelationship>
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// At least one value is floating point use Double.
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| _ ->
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let dbl1 =
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try
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Convert.ToDouble value1
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with
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| :? OverflowException ->
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printfn "value1 is outside the range of a Double."
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0.
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| _ -> 0.
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let dbl2 =
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try
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Convert.ToDouble value2
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with
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| :? OverflowException ->
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printfn "value2 is outside the range of a Double."
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0.
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| _ -> 0.
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dbl1.CompareTo dbl2 |> enum<NumericRelationship>
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// </Snippet1>
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// <Snippet2>
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printfn $"{Utility.isNumeric 12}"
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printfn $"{Utility.isNumeric true}"
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printfn $"{Utility.isNumeric 'c'}"
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printfn $"{Utility.isNumeric (DateTime(2012, 1, 1))}"
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printfn $"{Utility.isInteger 12.2}"
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printfn $"{Utility.isInteger 123456789}"
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printfn $"{Utility.isFloat true}"
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printfn $"{Utility.isFloat 12.2}"
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printfn $"{Utility.isFloat 12}"
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printfn $"{12.1} {Utility.compare 12.1 12} {12}"
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// The example displays the following output:
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// True
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// False
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// False
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// False
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// False
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// True
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// False
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// True
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// False
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// 12.1 GreaterThan 12
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// </Snippet2>

‎snippets/fsharp/System/ValueType/Overview/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="example1.fs" />
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</ItemGroup>
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</Project>

‎snippets/fsharp/System/ValueType/ToString/ToString2.fs‎

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// <Snippet1>
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namespace Corporate.EmployeeObjects
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[<Struct>]
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type EmployeeA =
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val mutable Name : string
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[<Struct>]
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type EmployeeB =
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val mutable Name : string
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override this.ToString() =
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this.Name
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module Example =
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let empA = EmployeeA(Name="Robert")
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printfn $"{empA}"
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let empB = EmployeeB(Name="Robert")
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printfn $"{empB}"
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// The example displays the following output:
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// Corporate.EmployeeObjects.EmployeeA
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// Robert
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// </Snippet1>

‎snippets/fsharp/System/ValueType/ToString/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="ToString2.fs" />
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</ItemGroup>
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</Project>

‎xml/System/ValueType.xml‎

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Aside from serving as the base class for value types in the .NET Framework, the <xref:System.ValueType> structure is generally not used directly in code. However, it can be used as a parameter in method calls to restrict possible arguments to value types instead of all objects, or to permit a method to handle a number of different value types. The following example illustrates how <xref:System.ValueType> prevents reference types from being passed to methods. It defines a class named `Utility` that contains four methods: `IsNumeric`, which indicates whether its argument is a number; `IsInteger`, which indicates whether its argument is an integer; `IsFloat`, which indicates whether its argument is a floating-point number; and `Compare`, which indicates the relationship between two numeric values. In each case, the method parameters are of type <xref:System.ValueType>, and reference types are prevented from being passed to the methods.
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:::code language="csharp" source="~/snippets/csharp/System/ValueType/Overview/example1.cs" id="Snippet1":::
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:::code language="fsharp" source="~/snippets/fsharp/System/ValueType/Overview/example1.fs" id="Snippet1":::
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:::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.valuetype.structure/vb/example1.vb" id="Snippet1":::
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The following example illustrates calls to the methods of the `Utility` class.
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:::code language="csharp" source="~/snippets/csharp/System/ValueType/Overview/example1.cs" id="Snippet2":::
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:::code language="fsharp" source="~/snippets/fsharp/System/ValueType/Overview/example1.fs" id="Snippet2":::
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:::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.valuetype.structure/vb/example1.vb" id="Snippet2":::
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]]></format>
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:::code language="cpp" source="~/snippets/cpp/VS_Snippets_CLR/ValueType.Equals Example/CPP/source.cpp" id="Snippet1":::
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:::code language="csharp" source="~/snippets/csharp/System/ValueType/Equals/source.cs" id="Snippet1":::
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:::code language="fsharp" source="~/snippets/fsharp/System/ValueType/Equals/source.fs" id="Snippet1":::
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:::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR/ValueType.Equals Example/VB/source.vb" id="Snippet1":::
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]]></format>
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:::code language="cpp" source="~/snippets/cpp/VS_Snippets_CLR/ValueType.Equals Example/CPP/source.cpp" id="Snippet1":::
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:::code language="csharp" source="~/snippets/csharp/System/ValueType/Equals/source.cs" id="Snippet1":::
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:::code language="fsharp" source="~/snippets/fsharp/System/ValueType/Equals/source.fs" id="Snippet1":::
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:::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR/ValueType.Equals Example/VB/source.vb" id="Snippet1":::
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]]></format>
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Value types defined by the `struct` keyword in C# and the `Structure`...`End Structure` construct in Visual Basic typically override the <xref:System.ValueType.ToString%2A?displayProperty=nameWithType> method to provide a more meaningful string representation of the value type. The following example illustrates the difference. It defines two value types, `EmployeeA` and `EmployeeB`, creates an instance of each, and calls its `ToString` method. Because the `EmployeeA` structure does not override the <xref:System.ValueType.ToString%2A?displayProperty=nameWithType> method, it displays only the fully qualified type name. The `EmployeeB.ToString` method, on the other hand, provides meaningful information about the object.
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:::code language="csharp" source="~/snippets/csharp/System/ValueType/ToString/ToString2.cs" interactive="try-dotnet" id="Snippet1":::
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:::code language="fsharp" source="~/snippets/fsharp/System/ValueType/ToString/ToString2.fs" id="Snippet1":::
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:::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/System.ValueType.ToString/vb/ToString2.vb" id="Snippet1":::
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Note that, although enumeration types are also value types, they derive from the <xref:System.Enum> class, which overrides <xref:System.ValueType.ToString%2A?displayProperty=nameWithType>.

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