TextBox setting caret at end of text

ormonds

I am trying to set the caret at the end of a textbox so it scrolls up as new lines get added. These are added by:

this.textBox1.Text += ThisText + System.Environment.NewLine;

However even though the value of this.textBox1.SelectionStart is correct (i.e. a large number), when I get to these lines:-

this.textBox1.SelectionStart = this.textBox1.Text.Length;
this.Refresh();

The textbox doesn't scroll. Can someone tell me what I am missing?

Dave Kreskowiak

As easy way to do this is to just call

textBox1.AppendText(ThisText + Environment.NewLine);

Stop putting this on everything. You don't need it as it's already implied.

Asking questions is a skill CodeProject Forum Guidelines Google: C# How to debug code Seriously, go read these articles.
Dave Kreskowiak

ormonds

Again, thank you.

Mycroft Holmes

Dave Kreskowiak wrote:

Stop putting this on everything.

That was my idea :-O to remind him where the control lives (he was creating a new form and lost the plot) Implied can be confusing the this newbie, thought it might help.

Never underestimate the power of human stupidity - RAH I'm old. I know stuff - JSOP

Dave Kreskowiak

Ah. I did not know.

Asking questions is a skill CodeProject Forum Guidelines Google: C# How to debug code Seriously, go read these articles.
Dave Kreskowiak

BillWoodruff

This is a swamp I have waded in, before. The cheap solution: put code to update the TextBox caret in the Form's 'Shown event handler. But, if you want to make the TextBox as independent as possible of its container, and, assuming: 1. this is a WinForm app with a TextBox set to show a vertical scrollbar 2. you will set the Text property at design time, or in the 'Load event of its container. 3. when the Form is shown, you want the TextBox scrolled to the end, and the TextBox selected/focused so if you start typing, what you type is added to the TextBox:

using System;
using System.Windows.Forms;

namespace YOURNAMESPACE
{
public partial class AutoScrolledTbx : UserControl // contains a TextBox
{
public AutoScrolledTbx()
{
InitializeComponent();
}

    // for use creating an instance in code at run-time
    public AutoScrolledTbx(string txt)
    {
        textBox1.Text = txt;

        this.textBox1.Select(this.textBox1.TextLength + 1, 0);
        this.textBox1.ScrollToCaret();
        this.textBox1.Capture = true;
        this.textBox1.Focus();
    }

    private void AutoScrolledTbx\_Load(object sender, EventArgs e)
    {
        // Marc Gravell
        this.BeginInvoke((MethodInvoker)this.ForceScroll);
    }

    // adapted from Marc Gravell
    // https://stackoverflow.com/a/218740/133321
    private void ForceScroll()
    {
        // UI thread update
        this.Invoke(
            (MethodInvoker)delegate
            {
                this.textBox1.Select(this.textBox1.TextLength + 1, 0);
                this.textBox1.ScrollToCaret();
                this.textBox1.Focus();
                ActiveControl = this.textBox1;
            }
        );
    }
    // public method to add text
    public void AppendText(string txt)
    {
        this.textBox1.AppendText(txt);
    }
}

}

Discussion: When a Form is being 'Loaded, then displayed, Controls may not appear in an expected state. By pushing a task onto the UI thread using Marc Gravell's technique shown here, you have achieved the equivalent of executing the update code in the Form's 'Shown event. In case you wonder why a UserControl is used here, rather than a sub-classed TextBox: a TextBox offers no 'Load or other initialization event to manipulate.

«