[Tips] How to "fix Cross-thread problem with C#" control (1/2)

If you use multi threading to improve the performance of your Windows Forms applications, you must make sure that you make calls to your controls in a thread-safe way.

To fix the cross-thread problem with C# control, you need to understand that you cannot access or modify a control from a thread other than the one that created it. This is because Windows Forms controls are not thread-safe, and doing so may cause errors or inconsistencies. To avoid this problem, you need to use a thread-safe way to call a control from another thread.

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Access to Windows Forms controls is not inherently thread safe. If you have two or more threads manipulating the state of a control, it is possible to force the control into an inconsistent state. Other thread-related bugs are possible, such as race conditions and deadlocks. It is important to make sure that access to your controls is performed in a thread-safe way.

If you use Thread on some day, You'll see this warning

It is unsafe to call a control from a thread other than the one that created the control without using the Invoke method. The following is an example of a call that is not thread safe.





- Label name lblSetup
- Progress Bar name pbInstalling

private delegate void DelegateProgressbar(); => this function define delegate method

Demo 1: Don't have parameters

 
/// <summary> 
/// Zidane, huuvi168@gmail.com
/// Run Control with Thread - Fix Cross Thread Problem
/// </summary>

private delegate void DelegateProgressbar();


private void RunControlWithInvoke()
{
           
     //If the cross thread calls
     if (InvokeRequired)
         pbInstalling.Invoke(new DelegateProgressbar(RunControlWithInvoke), null);
     else
     {
         pbInstalling.Style = ProgressBarStyle.Marquee;
         pbInstalling.MarqueeAnimationSpeed = 30;
         lblSetup.Text = "Installing ...";
     }
        
}


private void StopControlWithInvoke()
{
    //If the cross thread calls
    if (InvokeRequired)
        pbInstalling.Invoke(new DelegateProgressbar(StopControlWithInvoke), null);
    else
    {
        pbInstalling.MarqueeAnimationSpeed = 0;
        pbInstalling.Refresh();
        lblSetup.Text = "Hoàn Tất";
    }        
} 

Demo 2: With Parameters

private void SetText(string text)
{
 // InvokeRequired required compares the thread ID of the
 // calling thread to the thread ID of the creating thread.
 // If these threads are different, it returns true.
 if (this.textBox1.InvokeRequired)
 { 
  SetTextCallback d = new SetTextCallback(SetText);
  this.Invoke(d, new object[] { text });
 }
 else
 {
  this.textBox1.Text = text;
 }
}

Relative topic:
https://learn-tech-tips.blogspot.com/2015/11/how-to-fix-cross-thread-problem-CSharp.html

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