Question

我的代码中的最后一个字符串有问题。

这是我的代码：

private void comboLname_SelectedIndexChanged(object sender, EventArgs e)
{
            string conn = "Data Source=srv-db-02;Initial Catalog=rmsmasterdbtest;Persist Security Info=True;User ID=test;Password=*****";
            string Query = "select * from RMSCRMTest.dbo.sales where LastName= '" + comboLname.Text + "' ;";


            SqlConnection Myconn = new SqlConnection(conn);
            SqlCommand cmdDataBase = new SqlCommand(Query, Myconn);
            SqlDataReader Reader;
            try
            {
                Myconn.Open();
                Reader = cmdDataBase.ExecuteReader();
                while (Reader.Read())
                {
                    string ID = Reader.GetInt32(Reader.GetOrdinal("ID")).ToString();
                    string AccountNuber = Reader.GetString(Reader.GetOrdinal("AccountNumber")).ToString();
                    string Time = Reader.GetDateTime(Reader.GetOrdinal("Time")).ToString();
                    string Deposit = Reader.GetDecimal(Reader.GetOrdinal("Deposit")).ToString();
                    string slastname = Reader.GetString(Reader.GetOrdinal("lastname"));
                    string sstatus = Reader.GetString(Reader.GetOrdinal("status"));
                    txtid.Text = ID;
                    txtacnum.Text = AccountNuber;
                    txttime.Text = Time;
                    txtdeposit.Text = Deposit;
                    txtlname.Text = slastname;
                    txtstatus.Text = status;

                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                Myconn.Close();
            }
}

此问题显示，因为我在表中添加了另一列并为列创建了字符串字符串

sstatus = Reader.GetString(Reader.GetOrdinal("status"));

我得到的错误是

data为null此方法或属性无法在空值上调用

其他字符串工作正常。

Answer 1

您需要使用SqlDataReader.IsDBNull方法检查可空字段：

int statusIndex = Reader.GetOrdinal("status");
string sstatus = Reader.IsDBNull(statusIndex) ? null : Reader.GetString(statusIndex);

＆＃34;数据为空＆＃34;使用SqlDataReader时

1 个答案: