How do I highlight Text in a Textbox in a C# Winforms program?

Question

I have a C# Winforms program with multiple textboxes. I used the properties for each box to place text in them, explaining to the user what value goes in them. I want the text to highlight whenever a user selects that box. By either tabbing or mouse click. I won't have to do this if there's a way to display what value goes in the textbox somewhere outside of it.

I tried the Textbox.select method but it had no effect. The same with this.

Here's a Screenshot of my program.

My Code:

    private void grapplingText1_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
    {
        grapplingText1.SelectionStart = 0;
        grapplingText1.SelectionLength = grapplingText1.Text.Length;

Will this do, or is more required?

Answer 1

How about you assign ToolTip to TextBox and put all the "talk what textbox is for" inside that?

Just drag & drop ToolTip inside the Form. And then in each TextBox properties you should have additional entry in Misc section ToolTip on toolTip1 (or whatever it's name will be if you rename it).

Then when user hovers over TextBox (Read Only/Disabled TextBox doesn't seems to display ToolTips) and stops there for 1 second ToolTip should show with proper info.

You can eventually or even better have a Label next to TextBox saying what is is, but having a ToolTip is also a good idea to explain more information to user thru that.

For doing stuff with WaterMark so you don't have to go the long way by setting the events, taking care of SelectAll etc you could do it like this. Create new watermark.cs file and replace it with this code. Make sure you have changed namespace to match your program namespace.

#region
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

#endregion

namespace Watermark {
    public static class TextBoxWatermarkExtensionMethod {
        private const uint ECM_FIRST = 0x1500;
        private const uint EM_SETCUEBANNER = ECM_FIRST + 1;
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)] private static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, uint wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);
        public static void SetWatermark(this TextBox textBox, string watermarkText) {
            SendMessage(textBox.Handle, EM_SETCUEBANNER, 0, watermarkText);
        }
    }
}
   internal class WatermarkTextBox : TextBox {
    private const uint ECM_FIRST = 0x1500;
    private const uint EM_SETCUEBANNER = ECM_FIRST + 1;
    private string watermarkText;
    public string WatermarkText {
        get { return watermarkText; }
        set {
            watermarkText = value;
            SetWatermark(watermarkText);
        }
    }
    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)] private static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, uint wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);
    private void SetWatermark(string watermarkText) {
        SendMessage(Handle, EM_SETCUEBANNER, 0, watermarkText);
    }
}

In your Form you activate it like this:

textBoxYourWhatever.SetWatermark("Text that should display");

It stays there as long the TextBox is empty. When users gets into TextBox text disappears. It appears again when TextBox is cleaned (either by user or automatically). No need for any special events etc.

EDIT:

I've added also internal class WaterMarkTextBox which gives you an option to simply use new WaterMarkTexBox that becomes available in Designer. Then drag and drop it to your designer and use it. It behaves like normal textbox just gives you additional field WaterMarkText.

I still prefer the first method thou. Doesn't make you rebuild your gui again.

Answer 2

I think .select will work if you know the text amount you want to select.

Try .SelectAll(); It should work for you

Answer 3

You need to use the TextBox.Focus() to get the focus on your control, and if doesn't automatically work, then just call the SelectAll() method on the Enter() event.

private TextBox1_Enter(object sender, EventArgs e) {    
    TextBoxTextHighlight(sender, null);
}

private TextBox2_Enter(object sender, EventArgs e) {
    TextBoxTextHighlight(sender, null);
}

private TextBox3_Enter(object sender, EventArgs e) {
    TextBoxTextHighlight(sender, null);
}

// And so forth...

private void TextBoxTextHighlight(object sender, EventArgs e) {
    (sender as TextBox).SelectAll();
}

This method will allow you to call it from any TextBoxX_Enter() event handler.

Otherwise, you even could create a new UserControl, call it whatever you want upon creation, then, when created into your project, edit the code and replace the inheritence of UserControl class by the TextBox class, then define within it the default behaviour you would like to have on the Enter() event, like this call to the SelectAll() method, and make it protected virtual, and within the constructor, you may subscribe the event handler like so:

public partial class CustomTextBox : TextBox {
    public CustomTextBox() 
        : base() {
        this.Enter += new EventHandler(Enter);
    }

    protected virtual Enter(object sender, EventArgs e) {
        this.SelectAll();
    }
}

I wrote it on the fly, so perhaps a few modifications are required, but you may get the idea. But I do not advise you to do so unless it's really worthy doing it for your proper situation. The simpler the better, and the simplest is to create an event handler for each of your form's TextBoxes and then call the TextBoxTextHighlight() method.