Selection changed textbox value C#

Question

If datagrid no have rows in my textbox have values from last selected values...

Need help IF DATAGRID NO HAVE VALUES TEXTBOX EMPTY

Thank you

 

private void testDataGridView_SelectionChanged(object sender, EventArgs e)
       {

           if (testDataGridView.SelectedRows.Count > 0)
           {

           string test = testDataGridView.SelectedRows[0].Cells["columnname"].Value.ToString();

testTextBox.Text = test;

            }
        }