หน้า login มันรันไม่ผ่านอะค่ะ ExecuteScalar ฟ้องที่ตัวนี้อะค่ะ ช่วยหน่อยค่ะ

 protected void btnLogin_Click(object sender, EventArgs e)
    {
        System.Data.SqlClient.SqlConnection objConn;
        System.Data.SqlClient.SqlCommand objCmd;

        
        string strConnString;
        string strSQL;


        strConnString = WebConfigurationManager.ConnectionStrings["ProjectConnection"].ConnectionString;
        objConn = new System.Data.SqlClient.SqlConnection(strConnString);
        objConn.Open();

        
        int intNumRows = 0;
        strSQL = "SELECT Username_cu, Password_cu FROM Customer WHERE Username_cu = '" + this.UsernameTextBox.Text + "' AND [Password_cu] = '" + this.PasswordTextBox.Text + "' ";
        objCmd = new SqlCommand(strSQL, objConn);
        intNumRows = Convert.ToInt32(objCmd.ExecuteScalar());



        if (intNumRows > 0)
        {
            Session["strUser"] = this.UsernameTextBox.Text;
            Response.Redirect("Page1.aspx");
        }
        else
        {
            this.UsernameTextBox.Visible = false;
            this.PasswordTextBox.Visible = false;
            this.lblStatus.Text = "Username/Password is wrong.";


        }


       
	}