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ThreadStaticAttribute.xml
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<Type Name="ThreadStaticAttribute" FullName="System.ThreadStaticAttribute">
<TypeSignature Language="C#" Value="public class ThreadStaticAttribute : Attribute" />
<TypeSignature Language="ILAsm" Value=".class public auto ansi beforefieldinit ThreadStaticAttribute extends System.Attribute" FrameworkAlternate="dotnet-uwp-10.0;net-5.0;net-6.0;net-7.0;net-8.0;net-9.0;netcore-1.0;netcore-1.1;netcore-2.0;netcore-2.1;netcore-2.2;netcore-3.0;netcore-3.1;netstandard-1.0;netstandard-1.1;netstandard-1.2;netstandard-1.3;netstandard-1.4;netstandard-1.5;netstandard-1.6;netstandard-2.0;netstandard-2.1" />
<TypeSignature Language="DocId" Value="T:System.ThreadStaticAttribute" />
<TypeSignature Language="VB.NET" Value="Public Class ThreadStaticAttribute
Inherits Attribute" />
<TypeSignature Language="F#" Value="type ThreadStaticAttribute = class
 inherit Attribute" />
<TypeSignature Language="C++ CLI" Value="public ref class ThreadStaticAttribute : Attribute" />
<TypeSignature Language="ILAsm" Value=".class public auto ansi serializable beforefieldinit ThreadStaticAttribute extends System.Attribute" FrameworkAlternate="netframework-1.1;netframework-2.0;netframework-3.0;netframework-3.5;netframework-4.0;netframework-4.5;netframework-4.5.1;netframework-4.5.2;netframework-4.6;netframework-4.6.1;netframework-4.6.2;netframework-4.7;netframework-4.7.1;netframework-4.7.2;netframework-4.8;netframework-4.8.1" />
<AssemblyInfo>
<AssemblyName>System.Runtime</AssemblyName>
<AssemblyVersion>4.0.0.0</AssemblyVersion>
<AssemblyVersion>4.0.10.0</AssemblyVersion>
<AssemblyVersion>4.0.20.0</AssemblyVersion>
<AssemblyVersion>4.1.0.0</AssemblyVersion>
<AssemblyVersion>4.2.0.0</AssemblyVersion>
<AssemblyVersion>4.2.1.0</AssemblyVersion>
<AssemblyVersion>4.2.2.0</AssemblyVersion>
<AssemblyVersion>5.0.0.0</AssemblyVersion>
<AssemblyVersion>6.0.0.0</AssemblyVersion>
<AssemblyVersion>7.0.0.0</AssemblyVersion>
<AssemblyVersion>8.0.0.0</AssemblyVersion>
<AssemblyVersion>9.0.0.0</AssemblyVersion>
</AssemblyInfo>
<AssemblyInfo>
<AssemblyName>mscorlib</AssemblyName>
<AssemblyVersion>1.0.5000.0</AssemblyVersion>
<AssemblyVersion>2.0.0.0</AssemblyVersion>
<AssemblyVersion>2.0.5.0</AssemblyVersion>
<AssemblyVersion>4.0.0.0</AssemblyVersion>
</AssemblyInfo>
<AssemblyInfo>
<AssemblyName>netstandard</AssemblyName>
<AssemblyVersion>2.0.0.0</AssemblyVersion>
<AssemblyVersion>2.1.0.0</AssemblyVersion>
</AssemblyInfo>
<TypeForwardingChain>
<TypeForwarding From="mscorlib" FromVersion="4.0.0.0" To="System.Runtime" ToVersion="0.0.0.0" FrameworkAlternate="dotnet-uwp-10.0" />
<TypeForwarding From="netstandard" FromVersion="2.1.0.0" To="System.Runtime" ToVersion="5.0.0.0" FrameworkAlternate="net-5.0" />
<TypeForwarding From="netstandard" FromVersion="2.1.0.0" To="System.Runtime" ToVersion="6.0.0.0" FrameworkAlternate="net-6.0" />
<TypeForwarding From="netstandard" FromVersion="2.1.0.0" To="System.Runtime" ToVersion="7.0.0.0" FrameworkAlternate="net-7.0" />
<TypeForwarding From="netstandard" FromVersion="2.1.0.0" To="System.Runtime" ToVersion="8.0.0.0" FrameworkAlternate="net-8.0" />
<TypeForwarding From="netstandard" FromVersion="2.1.0.0" To="System.Runtime" ToVersion="9.0.0.0" FrameworkAlternate="net-9.0" />
<TypeForwarding From="System.Runtime" FromVersion="4.1.1.1" To="mscorlib" ToVersion="4.0.0.0" FrameworkAlternate="netframework-4.6.2;netframework-4.7;netframework-4.7.1;netframework-4.7.2;netframework-4.8;netframework-4.8.1" />
</TypeForwardingChain>
<Base>
<BaseTypeName>System.Attribute</BaseTypeName>
</Base>
<Interfaces />
<Attributes>
<Attribute>
<AttributeName Language="C#">[System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)]</AttributeName>
<AttributeName Language="F#">[<System.AttributeUsage(System.AttributeTargets.Field, Inherited=false)>]</AttributeName>
</Attribute>
<Attribute FrameworkAlternate="netframework-1.1;netframework-2.0;netframework-3.0;netframework-3.5;netframework-4.0;netframework-4.5;netframework-4.5.1;netframework-4.5.2;netframework-4.6;netframework-4.6.1;netframework-4.6.2;netframework-4.7;netframework-4.7.1;netframework-4.7.2;netframework-4.8;netframework-4.8.1">
<AttributeName Language="C#">[System.Serializable]</AttributeName>
<AttributeName Language="F#">[<System.Serializable>]</AttributeName>
</Attribute>
<Attribute FrameworkAlternate="netframework-2.0;netframework-3.0;netframework-3.5;netframework-4.0;netframework-4.5;netframework-4.5.1;netframework-4.5.2;netframework-4.6;netframework-4.6.1;netframework-4.6.2;netframework-4.7;netframework-4.7.1;netframework-4.7.2;netframework-4.8;netframework-4.8.1">
<AttributeName Language="C#">[System.Runtime.InteropServices.ComVisible(true)]</AttributeName>
<AttributeName Language="F#">[<System.Runtime.InteropServices.ComVisible(true)>]</AttributeName>
</Attribute>
</Attributes>
<Docs>
<summary>Indicates that the value of a static field is unique for each thread.</summary>
<remarks>
<format type="text/markdown"><![CDATA[
## Remarks
A `static` field marked with <xref:System.ThreadStaticAttribute> is not shared between threads. Each executing thread has a separate instance of the field, and independently sets and gets values for that field. If the field is accessed on a different thread, it will contain a different value.
Note that in addition to applying the <xref:System.ThreadStaticAttribute> attribute to a field, you must also define it as a `static` field (in C# or F#) or a `Shared` field (in Visual Basic).
> [!NOTE]
> Do not specify initial values for fields marked with `ThreadStaticAttribute`, because such initialization occurs only once, when the class constructor executes, and therefore affects only one thread. If you do not specify an initial value, you can rely on the field being initialized to its default value if it is a value type, or to `null` if it is a reference type.
Use this attribute as it is, and do not derive from it.
For more information about using attributes, see [Attributes](/dotnet/standard/attributes/).
## Examples
The following example instantiates a random number generator, creates ten threads in addition to the main thread, and then generates two million random numbers in each thread. It uses the <xref:System.ThreadStaticAttribute> attribute to calculate the sum and the count of random numbers per thread. It also defines two additional per-thread fields, `previous` and `abnormal`, that allows it to detect corruption of the random number generator.
:::code language="csharp" source="~/snippets/csharp/System/ThreadStaticAttribute/Overview/threadsafe2a.cs" id="Snippet1":::
:::code language="fsharp" source="~/snippets/fsharp/System/ThreadStaticAttribute/Overview/threadsafe2a.fs" id="Snippet1":::
:::code language="vb" source="~/snippets/visualbasic/VS_Snippets_CLR_System/system.threadstaticattribute/vb/threadsafe2a.vb" id="Snippet1":::
The example uses the `lock` statement in C#, the `lock` function in F#, and the `SyncLock` construct in Visual Basic to synchronize access to the random number generator. This prevents corruption of the random number generator, which typically results in its returning a value of zero for all subsequent calls.
The example also uses the <xref:System.Threading.CountdownEvent> class to ensure that each thread has finished generating random numbers before it displays the total number of calls. Otherwise, if the main thread completes execution before the additional threads that it spawns, it displays an inaccurate value for the total number of method calls.
]]></format>
</remarks>
<altmember cref="T:System.Attribute" />
<altmember cref="T:System.Threading.Thread" />
<altmember cref="T:System.Threading.AsyncLocal`1" />
<related type="Article" href="/dotnet/standard/attributes/">Extending Metadata Using Attributes</related>
<related type="Article" href="/dotnet/standard/threading/">Managed Threading</related>
</Docs>
<Members>
<Member MemberName=".ctor">
<MemberSignature Language="C#" Value="public ThreadStaticAttribute ();" />
<MemberSignature Language="ILAsm" Value=".method public hidebysig specialname rtspecialname instance void .ctor() cil managed" />
<MemberSignature Language="DocId" Value="M:System.ThreadStaticAttribute.#ctor" />
<MemberSignature Language="VB.NET" Value="Public Sub New ()" />
<MemberSignature Language="C++ CLI" Value="public:
 ThreadStaticAttribute();" />
<MemberType>Constructor</MemberType>
<AssemblyInfo>
<AssemblyName>System.Runtime</AssemblyName>
<AssemblyVersion>4.0.0.0</AssemblyVersion>
<AssemblyVersion>4.0.10.0</AssemblyVersion>
<AssemblyVersion>4.0.20.0</AssemblyVersion>
<AssemblyVersion>4.1.0.0</AssemblyVersion>
<AssemblyVersion>4.2.0.0</AssemblyVersion>
<AssemblyVersion>4.2.1.0</AssemblyVersion>
<AssemblyVersion>4.2.2.0</AssemblyVersion>
<AssemblyVersion>5.0.0.0</AssemblyVersion>
<AssemblyVersion>6.0.0.0</AssemblyVersion>
<AssemblyVersion>7.0.0.0</AssemblyVersion>
<AssemblyVersion>8.0.0.0</AssemblyVersion>
<AssemblyVersion>9.0.0.0</AssemblyVersion>
</AssemblyInfo>
<AssemblyInfo>
<AssemblyName>mscorlib</AssemblyName>
<AssemblyVersion>1.0.5000.0</AssemblyVersion>
<AssemblyVersion>2.0.0.0</AssemblyVersion>
<AssemblyVersion>2.0.5.0</AssemblyVersion>
<AssemblyVersion>4.0.0.0</AssemblyVersion>
</AssemblyInfo>
<AssemblyInfo>
<AssemblyName>netstandard</AssemblyName>
<AssemblyVersion>2.0.0.0</AssemblyVersion>
<AssemblyVersion>2.1.0.0</AssemblyVersion>
</AssemblyInfo>
<Parameters />
<Docs>
<summary>Initializes a new instance of the <see cref="T:System.ThreadStaticAttribute" /> class.</summary>
<remarks>To be added.</remarks>
</Docs>
</Member>
</Members>
</Type>