CODEWITHSUNDEEP
c#winformstextboxcustom-controlstextselection
Mauro Ganswer
Mauro Ganswer

Reputation: 1419

Prevent selecting text in a TextBox

Similar questions have been already asked (e.g., here), however I've not found an answer for my specific case. I'm building a custom control based on a DevExpress control, which in turns is based on standard TextBox and I've a flickering problem that seems due to the base TextBox component, which tries to update selection.

Without explaining all the details of my custom control, to reproduce the problem you just need to place a TextBox inside a Form and then use this code:

public partial class Form1 : Form {
    public Form1() {
        InitializeComponent();
        textBox1.MouseMove += TextBox1_MouseMove;
    }

    private void TextBox1_MouseMove(object sender, MouseEventArgs e) {
        (sender as TextBox).Text = DateTime.Now.Ticks.ToString();
    }
}

If you launch it, you click on the TextBox and then you move the cursor toward right you will notice the flickering problem (see video here). For my custom control I would need to avoid this flickering. I'm bound to use a TextBox (so no RichTextBox). Any idea?

Upvotes: 1

Views: 2770

Answers (3)

Mauro Ganswer
Mauro Ganswer

Reputation: 1419

The solution has been provided in the meantime by Reza Aghaei by overriding WndProc and intercepting WM_SETFOCUS messages. See here

Upvotes: 1

Dave S
Dave S

Reputation: 1009

Looking at the video it looks like your textbox is calling WM_ERASEBKGND unnecessarily. In order to remedy this problem you can subclass the textbox class and intercept these messages. Below is sample code which should do the trick (untested) Disclaimer: I have used this technique for other WinForm controls that had the type of flicker shown in your video but not TextBox. If it does work for you, please let me know. Good luck!

// textbox no flicker
public partial class TexttBoxNF : TextBox
{
    public TexttBoxNF()
    {
    }

    public TexttBoxNF(IContainer container)
    {
        container.Add(this);

        InitializeComponent();

        //Activate double buffering
        this.SetStyle(ControlStyles.OptimizedDoubleBuffer | ControlStyles.AllPaintingInWmPaint, true);

        //Enable the OnNotifyMessage event so we get a chance to filter out 
        // Windows messages before they get to the form's WndProc
        this.SetStyle(ControlStyles.EnableNotifyMessage, true);
    }

    //http://stackoverflow.com/questions/442817/c-sharp-flickering-listview-on-update
    protected override void OnNotifyMessage(Message m)
    {
        //Filter out the WM_ERASEBKGND message
        if (m.Msg != 0x14)
        {
            base.OnNotifyMessage(m);
        }
    }
}

Upvotes: 0

AdrianS
AdrianS

Reputation: 11

Depending on what u want to do there are several solutions:

If you want to prevent the selection it would be:

        private void TextBox1_MouseMove(object sender, MouseEventArgs e)
    {
        (sender as TextBox).Text = DateTime.Now.Ticks.ToString();
        (sender as TextBox).SelectionLength = 0;
    }

Or for selecting all:

        private void TextBox1_MouseMove(object sender, MouseEventArgs e)
    {
        (sender as TextBox).Text = DateTime.Now.Ticks.ToString();
        (sender as TextBox).SelectAll();
    }

And besides that u also could specify the conditions for selecting, for example:

        private void TextBox1_MouseMove(object sender, MouseEventArgs e)
    {
        (sender as TextBox).Text = DateTime.Now.Ticks.ToString();
        if (MouseButtons == MouseButtons.Left) (sender as TextBox).SelectAll();
        else (sender as TextBox).SelectionLength = 0;
    }

But as long as you want to select the text you always will get some flickering, because a normal Textbox has not the possibility to use things like BeginEdit and EndEdit and so it will change the text first and then select it.

Upvotes: 0

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