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I've always been under the impression that Thread.Abort was a pretty fast and dirty way to kill a thread. 
 
Is there a specific long running operation (eg a database call?) that causes the Abort to become less responsive?
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Yes - an ExecuteReader method call across a WAN against an Access database is very long-running and, apparently, the thread will wait until Access returns command before aborting it when Thread.Abort is called. &nbsp;I was hoping there was a P/Invoke system call that would kill the running thread immediately.
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I think you might actually be able to terminate a bit more gracefully... 
 
Have you considered requesting that the command stop executing using the DbCommand.Cancel method during your long query then aborting the thread?
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Can you offer an example, please? &nbsp;The ExecuteReader command is synchronous and I cannot move past that command once it has launched. &nbsp;From where would I call the Cancel method? &nbsp;From the calling thread or the running thread?
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Ok, usual sort of thing... I've set up a simple form with start and stop buttons 0 error handling and undoubtedly bug ridden. 
 
Start button is clicked and starts a long running process on a new thread so as not to block the UI. In my case I'm simulating this on SQL server as I don't have an access database to hand. 
Stop button can interrupt this process successfully as it runs on a separate thread to the executing command. 
 
Does a similar trick work for you with your access connection? 

<pre><code class="code-10 nolinks" id="code-121213">public partial class Form1 : Form
 {
 Thread longRunner = null;
 DbCommand executingCommand = null;
 bool isExecuting = false;
 
 public Form1()
 {
 InitializeComponent();
 }
 
 private void btnStop_Click(object sender, EventArgs e)
 {
 if (isExecuting)
 {
 executingCommand.Cancel();
 isExecuting = false;
 }
 if(longRunner != null){
 longRunner.Abort();
 longRunner = null;
 }
 MessageBox.Show(&quot;longRunner is dead.&quot;);
 }
 
 private void btnGo_Click(object sender, EventArgs e)
 {
 longRunner = new Thread(new ThreadStart(RunQuery));
 longRunner.Start();
 MessageBox.Show(&quot;longRunner started.&quot;);
 }
 
 private void RunQuery()
 {
 DbConnection conn = new OdbcConnection(@&quot;Driver={SQL Native Client};Server=SqlServer\Instance;Database=DB;Trusted_Connection=yes;&quot;);
 executingCommand = conn.CreateCommand();
 executingCommand.CommandText = &quot;WAITFOR DELAY '00:00:20'&quot;;
 try
 {
 conn.Open();
 isExecuting = true;
 executingCommand.ExecuteNonQuery();
 MessageBox.Show(&quot;executingCommand complete.&quot;);
 }
 finally
 {
 conn.Close();
 }
 }
 }
</code></pre>
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Thanks! &nbsp;I will try that to see if it works.
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No luck - the Cancel method also hangs, similar to Thread.Abort. &nbsp;I do not know enough about the JET database engine to know what exactly is happening when the ExecuteReader and Cancel methods are called, but both are non-responsive when executed over a WAN. 
 
It seems that what I need here is a mechanism, as first described, that will kill the thread unconditionally. &nbsp;Any thoughts?
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My last roll of the dice is that if you're trying to kill the thread in order to exit the application you could set the IsBackground property to true, which will stop the thread from stopping the app terminating.
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<div class="content wysiwyg-content">
Hello. &nbsp;I need to immediately kill a running thread in C# when the user clicks a command button. &nbsp;The thread migrates data from an Access database one row at a time and massages that data before moving into SQL server. &nbsp;How do I IMMEDIATELY kill that thread without using Thread.Abort (which waits for a &quot;safe&quot; exit point)? &nbsp;In other words, I need a command or function or P/Invoke call that I can use to stop thread processing absolutely immediately. &nbsp;I can clean up resources and locks myself after the thread has been killed but I cannot wait for Thread.Abort to do its thing. 
 
Thanks in advance for any assistance.
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</div>

Hello.  I need to immediately kill a running thread in C# when the user clicks a command button.  The thread migrates data from an Access database one row at a time and massages that data before moving into SQL server.  How do I IMMEDIATELY kill that thread without using Thread.Abort (which waits for a "safe" exit point)?  In other words, I need a command or function or P/Invoke call that I can use to stop thread processing absolutely immediately.  I can clean up resources and locks myself after the thread has been killed but I cannot wait for Thread.Abort to do its thing.

Thanks in advance for any assistance.

How do I IMMEDIATELY Kill A Running Thread?

The .NET Framework is not specific to any one programming language; rather, it includes a library of functions that allows developers to rapidly build applications. Several supported languages include C#, VB.NET, C++ or ASP.NET.