为什么保持返回 0 的结果？

蓝光3_5KY

我是 c# ASP.NET 的新手，我想用登录部分的值插入检查数据库值，我做的一切都是正确的，但是为什么当我输入相同的值时，我仍然继续发现该值不正确在我的数据库中...有什么想法吗？并且我的 dt 行数一直为 0...当我添加参数时有什么问题吗？

  SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\Ng\Documents\Visual Studio 2015\Projects\Assignment6\Assignment6\App_Data\photoCompetition.mdf;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFramework");

 protected void Button1_Click(object sender, EventArgs e)
        {
                con.Open();
                SqlCommand cmd = new SqlCommand("SELECT * FROM [User] WHERE email='@useremail' and password='@password'", con);
                cmd.Parameters.Add("@useremail", SqlDbType.Text).Value = emailtext.Text;
                cmd.Parameters.Add("@password", SqlDbType.Text).Value = passwordtext.Text;
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable();
                sda.Fill(dt);
                int i = cmd.ExecuteNonQuery();
                con.Close();

                if (dt.Rows.Count > 0)
                {
                    Response.Redirect("Membermenu.aspx");
                }
                else
                {
                    lblMsg.Text = "Your username and password is incorrect";
                    lblMsg.ForeColor = System.Drawing.Color.Red;
                    emailtext.Text = "";
                    passwordtext.Text = "";
                }
        }

克里希纳

使用参数时不需要将单引号设置为字符串，删除查询中的引号

SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\Users\Ng\Documents\Visual Studio 2015\Projects\Assignment6\Assignment6\App_Data\photoCompetition.mdf;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFramework");

 protected void Button1_Click(object sender, EventArgs e)
        {
                con.Open();
                SqlCommand cmd = new SqlCommand("SELECT * FROM [User] WHERE email=@useremail and password=@password", con);
                cmd.Parameters.Add("@useremail", SqlDbType.Varchar).Value = emailtext.Text;
                cmd.Parameters.Add("@password", SqlDbType.Varchar).Value = passwordtext.Text;
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable();
                sda.Fill(dt);
                int i = cmd.ExecuteNonQuery();
                con.Close();

                if (dt.Rows.Count > 0)
                {
                    Response.Redirect("Membermenu.aspx");
                }
                else
                {
                    lblMsg.Text = "Your username and password is incorrect";
                    lblMsg.ForeColor = System.Drawing.Color.Red;
                    emailtext.Text = "";
                    passwordtext.Text = "";
                }
        }

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