دوستان ممنونم ازتون این کد رو نوشتم
SqlCommand command10 = newSqlCommand("Select * from tblstore where isbn = '" + txtisbn.Text + "'", mycon3);
SqlDataReader reader1 = command10.ExecuteReader();
if (!reader1.Read())
{
}
if (reader1["sale_price"] != DBNull.Value)
{
double d = Convert.ToDouble(reader1["sale_price"].ToString());
su = d * Convert.ToDouble(txtnumber.Text);
txtsu.Text = su.ToString();
}
reader1.Close();
cmd3 = newSqlCommand("insert into Tblsale (sale_id,sale_date,isbn,number,username,customer_i d,comment,ts_price)values('" + @txtsale_id.Text + "','" + @txtsale_date.Text + "','" + @txtisbn.Text + "','" + @txtnumber.Text + "','" + @txtusername.Text + "','" + @txtcustomer_id.Text + "','" + @txtcomment.Text + "','" + @txtsu.Text + "'",mycon3);
int dr3 = cmd3.ExecuteNonQuery();
خط آخر این ارورو میده
'meghdar txtu.text'incorrect syntax near