//this is the method

private bool isInt(string strInput)
                {
                    int dataParse = 0;
                    if(int.TryParse(strInput, out dataParse) == true)
                 {
                    return true;
                 }
                 else
                 {
                    return false;
                 }
                }



//This is the code
 



if (txtFirstNumber.TextLength > 0 && txtSecondNumber.TextLength > 0)
            {
                int exp = 0;
                //Check that the second number is an integer
                try
                {

                    if (isInt(txtSecondNumber.Text) == true)
                    {
                        exp = Convert.ToInt32(txtSecondNumber.Text);
                    }
                    

                }
                //If it is not an integer, give an error
                catch (FormatException)
                {
                    MessageBox.Show("Second number must be an integert value.");
                    txtSecondNumber.Focus();

                }