Question

i am new user in devexpress WPF app. i really want to learn how to detect any changes on textbox event? For example; there are 2 textbox (devexpress) (txt1,txt2) . if i erase values on txt1, txt2 must erase own values.

like that:

  private void txt1_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Delete)
        {
            txt2.Text = String.Empty;
        }
    }

is it true? Can you help me?

Answer 1

If the text of txt2 has to be exactly the same like in txt1, use binding:

<TextBox Name="txt2" Text="{Binding ElementName=txt1, Path=Text}"/>

If you just want to get the changes, try this (using the TextChanged-Event instead of KeyDown, because you also can paste strings into textboxes):

string oldtext = "";
private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
    string removedstring = "";
    string addedstring = "";
    TextBox source = (TextBox)e.Source;
    TextChange t = e.Changes.First();

    if (t.RemovedLength > 0)
    {
        removedstring = oldtext.Substring(t.Offset, t.RemovedLength);
    }

    if (t.AddedLength > 0)
    {
        addedstring = source.Text.Substring(t.Offset, t.AddedLength);
    }

    oldtext = source.Text;
}

If you want to set txt2.Text = txt1.Text by code

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        TextBox source = (TextBox)e.Source;
        TextChange t = e.Changes.First();

        string first = txt2.Text.Substring(0, t.Offset);
        string added = source.Text.Substring(t.Offset, t.AddedLength);
        string last = (t.Offset+1>tbrt.Text.Length)?"":txt2.Text.Substring(t.Offset, txt2.Text.Length-1);
        last = last.Remove(0, t.RemovedLength);
        txt2.Text = first + added + last;
    }