如何验证我的sql数据库中是否已存在名字和姓氏 [英] how to validate if the first name and last name is already exist in my sql database

问题描述

如何验证我的sql数据库中是否已存在名字和姓氏我在temp = Convert.ToInt32（com.ExecuteScalar（）。ToString（））中有错误;

how to validate if the first name and last name is already exist in my sql database i have error in temp = Convert.ToInt32(com.ExecuteScalar().ToString());

SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["registrationConnectionString"].ConnectionString);
                conn.Open();

                
                string check = "select count(*) from userdata where FirstName,LastName='" +   TextBoxFN.Text + TextBoxFN.Text +"'";
                SqlCommand com = new SqlCommand(check, conn);
                com.Parameters.AddWithValue("@FN", TextBoxFN.Text);
                com.Parameters.AddWithValue("@LN", TextBoxLN.Text);
                temp = Convert.ToInt32(com.ExecuteScalar().ToString());

                if (temp == 1)
                {

                    Label1.Text = "Student Already Exist";

                }

推荐答案

用

Replace this line with

string check = "select count(*) from userdata where FirstName,LastName='" +   TextBoxFN.Text + TextBoxFN.Text +"'";

这个

With this

string check = string.formt("select count(*) from userdata where FirstName='{0}' AND LastName='{1}'", TextBoxFN.Text, TextBoxLN.Text);

您不需要使用参数化查询，因为您的查询已经包含值。所以让你的查询如下，然后运行它。

You need not to use parameterized query since your query already contains values. so make your query as follows and then run it.

conn.Open();
string inputQuery= "select count(*) from userdata where FirstName='" + TextBoxFN.Text         + "' And LastName='" + TextBoxFN.Text +"'";
SqlCommand com = New SqlCommand(inputQuery, conn);
temp = Convert.ToInt32(com.ExecuteScalar().ToString());
if (temp >= 1) '<--- updated here
  {
    Label1.Text = "Student Already Exist";
  }

否则你可以使用参数化查询：

or else you can use parameterized query as :

string check = "select count(*) from userdata where FirstName='{FN}' AND LastName='{LN}'"
SqlCommand com = new SqlCommand(check, conn);
com.Parameters.AddWithValue("@FN", TextBoxFN.Text);
com.Parameters.AddWithValue("@LN", TextBoxLN.Text);
temp = Convert.ToInt32(com.ExecuteScalar().ToString());

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