C# Get active TextBox and insert text at cursor

gistfile1.cs

            if (this.ActiveControl.GetType() == typeof(TextBox))
            {
                TextBox textBox = (TextBox)this.ActiveControl;
                String text = ((Label)sender).Text;
                int pos = textBox.SelectionStart;
                textBox.Text = textBox.Text.Insert(pos, text);
                //Fix cursor position
                textBox.Focus();
                textBox.SelectionStart = pos;
                textBox.SelectionLength = text.Length;
            }