CODE EXAMPLE FOR CSHARP

how to disable button until the value is selected c#

private void richTextBox1_SelectionChanged(object sender, EventArgs e)
{
    if (richTextBox1.SelectedText != null && !string.IsNullOrEmpty(richTextBox1.SelectedText))
        button2.Enabled = true;
    else
        button2.Enabled = false;
}