How do I fix this error in C# (system.invalidoperationexception)

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Hello guys I try to add text to my text box but didn't work and give this error:
System.InvalidOperationException: 'Cross-thread operation not valid: Control 'log_txtbox' accessed from a thread other than the thread it was created on

What I have tried:

private void Events_ClientDisconnected(object sender, ClientDisconnectedEventArgs e)
{
    log_txtbox.Text += Environment.NewLine + DateTime.Now.ToString() + e.IpPort + " : " + "quit";
}

Posted 16-Mar-21 21:33pm

daniel honarpishe

Updated 16-Mar-21 22:20pm

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#realJSOP · Accepted Answer · 2021-03-16T22:20:00

Solution 1

You can't update the UI from another thread. Depending on whether you're using WinForms or WPF, the solution is different.

WinForms:

C#

log_txtbox.Invoke(() => 
{
    log_txtbox.Text += .....;
});

WPF:

C#

this.Dispatcher.Invoke(()=>
{
    log_txtbox.Text += ....;
});

Posted 16-Mar-21 22:20pm

#realJSOP

Comments

daniel honarpishe 17-Mar-21 4:36am

now give me this error: CS1660
my code :
log_txtbox.Invoke(() =>
{
log_txtbox.Text += Environment.NewLine+ DateTime.Now.ToString()+ e.IpPort.ToString()+" : "+"join";
});

#realJSOP 17-Mar-21 4:46am

Try doing this:

log_txtbox.Text = string.Concat(log_txtbox.Text, Environment.NewLine, DateTime.Now.ToString(), e.IpPort.ToString())," : join");

daniel honarpishe 17-Mar-21 5:01am

," : "," : join"; now give here error

#realJSOP 17-Mar-21 5:11am

I gotta say, be a programmer. I corrected my reply when I realized I had made that error, but it would have been just as simple for you to do it on your own.

Maciej Los 17-Mar-21 4:47am

5ed!