Question

I’ve got my main form Form1 running the main bulk of my program.

I have a separate thread started to perform an algorithm.

When I run the method from the new thread, method MyAlgorithm() I get the error

InvalidOperationException with the message, “Control control name accessed from a thread other than the thread it was created on.”

How do I get back to the original thread so that I can run the method to update my text boxes with the latest values?

This is the method that I want to run contained in Form1, the main class in my application.

// Reset the results values
public void ShowResults()
{
    while (true)
    {

        loopsNum.Text = Convert.ToString(resultLoopsNum);
        nodesVisitedNum.Text = Convert.ToString(resultNodesVisitedNum);
        nodesResolvedNum.Text = Convert.ToString(resultNodesResolvedNum);
        cpuLoopsNum.Text = Convert.ToString(resultCpuLoopsNum);
        shortestPathCostNum.Text = Convert.ToString(resultShortestPathCost);

    } 
}

I’ve looked at the Invoke() methods, but I don’t know how to get the original instance of my Form1 from the threaded method.

I’m invoking my thread like this…

        // Set the algorithm method up in it's own thread
        Thread thread = new Thread(new ThreadStart(MyAlgorithm));

        // Run the algorithm
        thread.Start();

Answer 1

Have a look at Control.Invoke():

public void ShowResults()
{
  while (true)
  {
    Thread.Sleep(1000); // don't spam the UI thread

    if (this.InvokeRequired) 
    {
      this.Invoke((Action)UpdateGui);
    }  
    else
    {
      UpdateGui();
    }
  } 
}

private void UpdateGui() 
{  
  loopsNum.Text = Convert.ToString(resultLoopsNum);
  nodesVisitedNum.Text = Convert.ToString(resultNodesVisitedNum);
  nodesResolvedNum.Text = Convert.ToString(resultNodesResolvedNum);
  cpuLoopsNum.Text = Convert.ToString(resultCpuLoopsNum);
  shortestPathCostNum.Text = Convert.ToString(resultShortestPathCost);
}