CODEWITHSUNDEEP
c#.netwinformsmultithreading
The Mask
The Mask

Reputation: 17427

setting new value to an label in thread execution

it's possible? I need for example,set new value to an label in thread execution.
I tried this: 

private void button1_Click_1(object sender, EventArgs e)
{
  Thread th = new Thread(new ThreadStart(DoWork));
  th.Start();
}

public void DoWork()
{
    while (true)
    {
        StartSearch(path, ref httpRequest);
    }
}

   public void StartSearch(string path, ref HttpWebRequest httpRequest) {
                  foo.GetTopic(path, delegate(string post, string name, string uid)
                  {
                      {
                          if (post.Contains("<font color=\"#0000FF\">"))
                          {
                              string msg = string.Format("Post:{0}\r\nby {1}({2})", post, name, uid);
                              //MessageBox.Show(msg);
                              labelX.text = msg;
                          }
                      }
                  }
              );
      }

I'm getting the following error:

Cross-thread operation not valid: Control 'labelX' accessed from a thread other than the thread it was created on.

How I do this? Thanks in advance!

Upvotes: 0

Views: 6117

Answers (5)

SHO
SHO

Reputation: 25

I also had this problem. Eventually solved.

Do not try to do everything in the textbox, but just think about the Msg you want to send to the textbox box.

MY CODE:

private delegate void _deleSetMesssage(string msg);

public void SetMessage(string msg)
{
    if (this.InvokeRequired)
    {
       _deleSetMesssage method = new _deleSetMesssage(SetMessage);
       this.Invoke(method, new object[] { msg });
    }
    else
    {
        this.label1.Text = msg;
    }
}

Not preferred Method:

CheckForIllegalCrossThreadCalls = false;

Upvotes: 0

SSS
SSS

Reputation: 1

You can use a background worker. In report progress, change the label value.

Upvotes: -1

dknaack
dknaack

Reputation: 60448

You have to invoke it to ensure that the ui thread (the thread who has created your label) does it. Its easy, try the following...

    delegate void SetLabel(string msg);

    void SetLabelMethod(string msg)
    {
        labelX.text = msg;
    }


this.Invoke(new SetLabel(SetLabelMethod), new object { msg }); // this is your form

Upvotes: 4

bug
bug

Reputation: 101

labelX.Invoke(new Action(() => labelX.Text = msg));

Upvotes: 1

Otiel
Otiel

Reputation: 18743

Call a delegate in your new thread, using an anonymous method:

this.Invoke((MethodInvoker) delegate {
    labelX.Text = msg;
});

Upvotes: 3

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