Convert string to decimal number

Question

Hi,

 

I do try many time to save decimal number into my database but there is erro saying that its cannot save string number. My database has two column (debit and credit) with number type. But when click to save its doesnt and stuck on line I coulored in red.

 

if (conn.State != ConnectionState.Open)
                conn.Open();
            SqlCommand comm = new SqlCommand();
            comm.Connection = conn;
            SqlParameter debit = new SqlParameter("@debit", SqlDbType.Decimal);
            SqlParameter credit = new SqlParameter("@credit", SqlDbType.Decimal);
            comm.Parameters.Add(debit);
            comm.Parameters.Add(credit);
            debit.Value = Convert.ToDecimal(txtDebit.Text, CultureInfo.InvariantCulture);  //its stucks here
            credit.Value = Convert.ToDecimal(txtCredit.Text, CultureInfo.InvariantCulture);  //its stucks here
            comm.Connection = conn;

            comm.CommandText = "insert into pay ([debit],[credit])values(@debit,@credit)";
            {
                if (MessageBox.Show("Are you sure to save?", "Save", MessageBoxButtons.YesNo) == DialogResult.Yes)
                {
                    try
                    {
                        comm.ExecuteNonQuery();
                    }

                    finally
                    {
                        conn.Close();
}