Bitterblue Bitterblue -4 years ago 106
C# Question

How to get the NEW text in TextChanged?

In a TextBox I'm monitoring the text changes. I need to check the text before doing some stuff. But I can only check the old text in the moment. How can I get the new Text ?

private void textChanged(object sender, EventArgs e)
{
// need to check the new text
}


I know .NET Framework 4.5 has the new
TextChangedEventArgs
class but I have to use .NET Framework 2.0.

Answer Source

Getting the NEW value

You can just use the Text property of the TextBox. If this event is used for multiple text boxes then you will want to use the sender parameter to get the correct TextBox control, like so...

private void textChanged(object sender, EventArgs e)
{
    TextBox textBox = sender as TextBox;
    if(textBox != null)
    {
        string theText = textBox.Text;
    }
}

Getting the OLD value

For those looking to get the old value, you will need to keep tract of that yourself. I would suggest a simple variable that starts out as empty, and changes at the end of each event:

string oldValue = "";
private void textChanged(object sender, EventArgs e)
{
    TextBox textBox = sender as TextBox;
    if(textBox != null)
    {
        string theText = textBox.Text;

        // Do something with OLD value here.

        // Finally, update the old value ready for next time.
        oldValue = theText;
    }
}

You could create your own TextBox control that inherits from the built-in one, and adds this additional functionality, if you plan to use this a lot.

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