'='附近的语法不正确。在System.Data.SqlClient.SqlConnection.OnError（SqlException异常

Question

我有问题，当我计算从会话[“ email”]获得的电子邮件的数量列值时，在尝试捕获错误之前，我会尝试int count =（int）cmd.ExecuteScalar（）; ，这是他们的错误消息“ System.Data.SqlClient.SqlConnection.OnError（SqlException异常时，'='附近的语法不正确。”。我需要从表中计算数量。menu_quantity的数据类型为float。

 protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["email"] != null)
        {
            A();
            //lbltotalitemcart.Text = A().ToString();
        }
        else
        {
            lbltotalitemcart.Text = "login email first";
        }

    }

---

 public int A()
    {
        String email = Request.QueryString["email"];
        string stmt = "SELECT COUNT(menu_quantity) FROM cart Where email=" + email + "";
        try
        {
            using (SqlConnection con = new SqlConnection(ConfigurationManager.
           ConnectionStrings["connectionString"].ConnectionString))
            {
                using (SqlCommand cmd = new SqlCommand(stmt, con))
                {
                    con.Open();
                    int count = (int)cmd.ExecuteScalar();
                    return count;
                }
            }
        }
        catch (Exception e)
        {
            lbltotalitemcart.Text = e.ToString();
            return 0;
        }
    }

Answer 1

您在'前后都错过了email：

SELECT COUNT(menu_quantity) FROM cart Where email='" + email + "'";

但是，这不是执行查询的好方法。而是使用SqlCommand.Parameters：

string stmt = "SELECT COUNT(menu_quantity) FROM cart Where email=@email"
 using (SqlConnection con = new SqlConnection(ConfigurationManager.
           ConnectionStrings["connectionString"].ConnectionString))
 {
       SqlCommand cmd = new SqlCommand(stmt, con)
       cmd.Parameters.Add("@email", SqlDbType.VarChar).Value = email;
       con.Open();
       int count = (int)cmd.ExecuteScalar();
       return count;
 }

Answer 2

我对ASP语法不太熟悉。但是我的直觉SQL知识告诉我您在查询本身中缺少电子邮件中的引号。