Question

我在程序中使用if else语句检查此错误。我有两件事需要检查。他们是

PoliceID（PK）
NRIC

下面的语句检查文本框是否具有与数据库中的PoliceID和NRIC相同的值。

if (tbpid.Text.Equals(dr["policeid"].ToString().Trim()) && (tbnric.Text.Equals(dr["nric"].ToString().Trim())))
                {

                    lbmsg.Text = "This police account has already exist. Please verify the details again.";

                }

如果文本框（police id）具有与数据库中相同的值，则它们将给出另一个不同的错误。

 if (tbpid.Text.Equals(dr["policeid"].ToString()))
                {
                    lbmsg.Text = "This police ID has already exists. Please generate another Police ID";
                }

如果文本框（NRIC）具有与数据库中相同的值，则它们将给出另一个错误

if (tbnric.Text.Equals(dr["nric"].ToString()))
                {
                    lbmsg.Text  ="This NRIC has already exist. Please ensure that the NRIC is correct";
                }

如果我将所有错误检查消息组合在一起就会是这样的。

 protected void btnAdd_Click(object sender, EventArgs e)
    {



            SqlConnection con = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI");
            con.Open();
            SqlCommand select = new SqlCommand("Select policeid, nric from PoliceAccount where policeid = @policeid" , con);
            SqlDataReader dr;

            select.Parameters.AddWithValue("@policeid", tbpid.Text);            

            dr = select.ExecuteReader();
            if(dr.Read())
            {
                if (tbpid.Text.Equals(dr["policeid"].ToString().Trim()) && (tbnric.Text.Equals(dr["nric"].ToString().Trim())))
                {

                    lbmsg.Text = "This police account has already exist. Please verify the details again.";

                }
                else if (tbpid.Text.Equals(dr["policeid"].ToString()))
                {
                    lbmsg.Text = "This police ID has already exists. Please generate another Police ID";
                }
                else if (tbnric.Text.Equals(dr["nric"].ToString()))
                {
                    lbmsg.Text  ="This NRIC has already exist. Please ensure that the NRIC is correct";
                }

            }

            else
            {

                SqlConnection conn = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI");
                conn.Open();
                SqlCommand cmd = new SqlCommand("insert into PoliceAccount(policeid, password, nric, fullname, postedto)  values('" + tbpid.Text.Trim() + "','" + tbpid.Text.Trim() + "','" + tbnric.Text.Trim() + "','" + tbfullname.Text.Trim() + "', '" + ddllocation.SelectedValue + "')", conn);
                cmd.ExecuteNonQuery();
                conn.Close();

                lbmsg.Text = "Congratulations. The police account of ID " + tbpid.Text + " has been successfully added. You may edit the profile via the edit profile tab above";

                tbpid.Text = "";
                tbnric.Text = "";
                tbfullname.Text = "";
                ddllocation.SelectedValue = "Select Location";


            }

            //ConfirmButtonExtender2.ConfirmText = "Are you sure you want to add this Police Account " + tbpid.Text + " ?";
        }

    }

但问题是，错误检查消息的前两个语句设法工作。不幸的是，NRIC的一个没有用。例如，如果我要键入不同的policeID但是相同的NRIC，则数据仍然被插入到数据库中，这意味着它完全忽略了上面的NRIC错误检查。我已经看了几个小时，我还没有找到问题。如果有人能指导我，我将不胜感激。

要添加，在我的数据库中，我已将主键设置为 policeID ，而 NRIC 只是常规我的数据库中的数据列

问候。

Answer 1

由于此查询

，最后一个无法正常工作

Select policeid, nric from PoliceAccount where policeid=@policeid 这不会返回任何行，因为ploiceid不存在意味着dr.Read()是假的，因为没有要读取的行，所以它直接进入你在数据库中插入数据的else部分。所以要使它工作。试试这个......

 if(dr.Read())
            {
                if (tbpid.Text.Equals(dr["policeid"].ToString().Trim()) && (tbnric.Text.Equals(dr["nric"].ToString().Trim())))
                {

                    lbmsg.Text = "This police account has already exist. Please verify the details again.";

                }
                else if (tbpid.Text.Equals(dr["policeid"].ToString()))
                {
                    lbmsg.Text = "This police ID has already exists. Please generate another Police ID";
                }
            }

            else
            {
 if (tbnric.Text.Equals(dr["nric"].ToString()))
                {
                    lbmsg.Text  ="This NRIC has already exist. Please ensure that the NRIC is correct";
                }
else
{

                SqlConnection conn = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI");
                conn.Open();
                SqlCommand cmd = new SqlCommand("insert into PoliceAccount(policeid, password, nric, fullname, postedto)  values('" + tbpid.Text.Trim() + "','" + tbpid.Text.Trim() + "','" + tbnric.Text.Trim() + "','" + tbfullname.Text.Trim() + "', '" + ddllocation.SelectedValue + "')", conn);
                cmd.ExecuteNonQuery();
                conn.Close();

                lbmsg.Text = "Congratulations. The police account of ID " + tbpid.Text + " has been successfully added. You may edit the profile via the edit profile tab above";

                tbpid.Text = "";
                tbnric.Text = "";
                tbfullname.Text = "";
                ddllocation.SelectedValue = "Select Location";
}
}

要使现有代码正常运行，请尝试此查询

Select policeid, nric from PoliceAccount where policeid=@policeid or nric=@nric

如果其中一个id存在于数据库中，它将始终返回行，如果两者都没有插入到数据库中。

Answer 2

您的选择语句似乎是个问题。看起来您希望nric也是唯一的，但您不会在select语句的where子句中使用它。你现在的方式，只要警察是独一无二的，任何nric值都可以。换句话说，如果前两个检查通过，那么第三个检查也将通过。试试这个：

SqlCommand select = new SqlCommand("Select policeid, nric from PoliceAccount where policeid = @policeid or nric = @nric" , con);
SqlDataReader dr;

select.Parameters.AddWithValue("@policeid", tbpid.Text);
select.Parameters.AddWithValue("@nric", tbnric.Text);

dr = select.ExecuteReader();

但是如果你不希望nric是唯一的，那么你的代码工作正常！

跳过一个错误检查if else语句

2 个答案: