Getting the thread ID from a thread

Question

In C  when debugging threads for example  you can see each thread s ID   I couldn t find a way to get that same thread  programmatically  I could not even get the ID of the current thread  in the properties of the Thread currentThread    So  I wonder how does Visual Studio get the IDs of the threads  and is there a way to get the handle of the thread with id 2345  for example

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GetThreadId returns the ID of a given native thread  There are ways to make it work with managed threads  I m sure  all you need to find is the thread handle and pass it to that function   GetCurrentThreadId returns the ID of the current thread    GetCurrentThreadId has been deprecated as of  NET 2 0  the recommended way is the Thread CurrentThread ManagedThreadId property

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You can use the deprecated AppDomain GetCurrentThreadId to get the ID of the currently running thread  This method uses a PInvoke to the Win32 API method GetCurrentThreadID  and will return the Windows thread ID   This method is marked as deprecated because the  NET Thread object does not correspond to a single Windows thread  and as such there is no stable ID which can be returned by Windows for a given  NET thread    See configurator s answer for more reasons why this is the case

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To get the OS ID use   AppDomain GetCurrentThreadId

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To find the current thread Id use -  Thread CurrentThread ManagedThreadId   But in this case you might need the current win32 thread id - use pInvoke to get it with this function    DllImport  Kernel32   EntryPoint    GetCurrentThreadId   ExactSpelling   true   public static extern Int32 GetCurrentWin32ThreadId      First you ll need to save the managed thread id and win32 thread id connection - use a dictionary that maps a win32 id to managed thread     Then to find a thread by it s id iterate over the process s thread using Process GetCurrentProcess   Threads and find the thread with that id   foreach  ProcessThread thread in Process GetCurrentProcess   Threads         var managedThread   win32ToManagedThread thread id        if  managedThread ManagedThreadId    threadId                  return managedThread

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From managed code you have access to instances of the Thread type for each managed thread  Thread encapsulates the concept of an OS thread and as of the current CLR there s a one-to-one correspondance with managed threads and OS threads  However  this is an implementation detail  that may change in the future    The ID displayed by Visual Studio is actually the OS thread ID  This is not the same as the managed thread ID as suggested by several replies    The Thread type does include a private IntPtr member field called DONT USE InternalThread  which points to the underlying OS structure  However  as this is really an implementation detail it is not advisable to pursue this IMO  And the name sort of indicates that you shouldn t rely on this

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For those about to hack       public static int GetNativeThreadId Thread thread                var f   typeof Thread  GetField  DONT USE InternalThread               BindingFlags GetField   BindingFlags NonPublic   BindingFlags Instance            var pInternalThread    IntPtr f GetValue thread           var nativeId   Marshal ReadInt32 pInternalThread   IntPtr Size    8    548   348      found by analyzing the memory         return nativeId

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System Threading Thread CurrentThread Name  System Threading Thread CurrentThread ManagedThreadId

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You can use Thread GetHashCode  which returns the managed thread ID  If you think about the purpose of GetHashCode  this makes good sense -- it needs to be a unique identifier  e g  key in a dictionary  for the object  the thread    The reference source for the Thread class is instructive here   Granted  a particular  NET implementation may not be based on this source code  but for debugging purposes I ll take my chances    GetHashCode  provides this hash code for algorithms that need quick checks of object equality   so it is well-suited for checking Thread equality -- for example to assert that a particular method is executing on the thread you wanted it called from

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The offset under Windows 10 is 0x022C  x64-bit-Application  and 0x0160  x32-bit-Application    public static int GetNativeThreadId Thread thread        var f   typeof Thread  GetField  DONT USE InternalThread           BindingFlags GetField   BindingFlags NonPublic   BindingFlags Instance        var pInternalThread    IntPtr f GetValue thread       var nativeId   Marshal ReadInt32 pInternalThread   IntPtr Size    8    0x022C   0x0160      found by analyzing the memory     return nativeId

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In C  when debugging threads for example  you can see each thread s ID   This will be the Ids of the managed threads   ManagedThreadId is a member of Thread so you can get the Id from any Thread object   This will get you the current ManagedThreadID  Thread CurrentThread ManagedThreadId  To get an OS thread by its OS thread ID  not ManagedThreadID   you can try a bit of linq  int unmanagedId   2345  ProcessThread myThread    from ProcessThread entry in Process GetCurrentProcess   Threads    where entry Id    unmanagedId     select entry  First     It seems there is no way to enumerate the managed threads and no relation between ProcessThread and Thread  so getting a managed thread by its Id is a tough one  For more details on Managed vs Unmanaged threading  see this MSDN article

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According to MSDN      An operating-system ThreadId has no   fixed relationship to a managed   thread  because an unmanaged host can   control the relationship between   managed and unmanaged threads    Specifically  a sophisticated host can   use the CLR Hosting API to schedule   many managed threads against the same   operating system thread  or to move a   managed thread between different   operating system threads    So basically  the Thread object does not necessarily correspond to an OS thread - which is why it doesn t have the native ID exposed

[c#] Getting the thread ID from a thread

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