无法完全清除RichTextBox

Question

I have a RichTextBox onto which I write long lists of data using a simple write method (see down)

I use vertical scrolbar, and writing and clearing is fine. The problem is with new text after clearing the text.

I use textbox.clear(); which clears the box OK, but when new text arrives, the old (cleared!) text shows up again, followed by the new text.

I have also tried: ResetText, Refresh, Update. dispose, Text =" , richTextBox.Document.Blocks.Clear(); (dont have that one). Have also tried new textbox = new textbox, all for no avail.

The text shows again and again, until I reset the application. I have seen several form threads on that one, but non helped.

My guess: I use both scroll bars. A scrollbar must have a buffer, The data is kept somewhere in the active scrollbar buffer?

Any (good) idea will be blessed.

This is how I write / erase the text in the richtextbox: (simplified. mainDisplay is a RichTextBox)

 public void mainDisplayText(string text)
    {
            this.mainDisplay.AppendText(text);
            this.mainDisplay.ScrollToCaret();
    }  

private void btnClear_Click(object sender, EventArgs e)
    {
       //Have tried all these options:
        this.mainDisplay.Text = "";  //or
        this.mainDisplay.Clear();    //or
        this.mainDisplay.SelectAll();     //or
        this.mainDisplay.SelectedText = "";
    }

Answer 1

You're reusing the same string, so:

this.mainDisplay.Clear();
text = string.Empty;

Should do the trick :)

Answer 2

Strange indeed. Could this be some issue in .net 4.7.x ? Since last week I compile everything in 4.7.2 and this problem has surfaced here also. Clear() seems to bring back the .Text content. So a Clear() after Text="" does not work.