Invoking with textbox c#

Question

Part of my program uses an event handler for the receive data of my serial port. The idea is when data is received that the text received is then added to the textbox (rx). I did not used to have this problem but something has changed and I can't figure out what. So now I am re-examining the way this is handled. During the form load of my winform the last thing I do is ``` if (!serialPort1.IsOpen) { serialPort1.Open(); serialPort1.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler); } ``` Then I have the event handler ``` private void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e) { string indata1 = serialPort1.ReadExisting(); // rx.Text = " "; accidentally posted this. it was from trial and error. rx.AppendText(Environment.NewLine + indata1); } ``` When I run the program it stops at the `rx.AppendText(Environment.NewLine + indata1);` and gives the error invalidoperationexception was unhandled: Control "accessed from a thread other than the threa…

Accepted Answer

Usually the exception you're seeing occurs when you run in debug mode, and if you run your application in release mode, you're unlikely to see the exception.

However, it is best to use invoke, as you have read. Something like this:

```
    private delegate void RefreshTextBox();

private void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e) {
        //this event is raised in an event separate from UI thread, 
        //so InvokeRequired must be checked and Invoke called to update UI controls. 
        if (this.InvokeRequired) {
            RefreshTextBox d = new RefreshTextBox(RefreshTextBoxResults);
            Invoke(d);
        } else {
            RefreshTextBoxResults();
        }
    }

private void RefreshTextBoxResults() {
        string indata1 = serialPort1.ReadExisting();
        rx.Text = " ";
        rx.AppendText(Environment.NewLine + indata1);
    }
```

The first time you see this invoke stuff, it's nearly impossible to follow, but take a close look and give it some time and it will make sense. Promise. :)

Invoking with textbox c#

Solution

Problem