为什么我需要一个局部变量来将SqlParameter中的值从Ajax存储到WCF方法

Question

I'm currently work with WCF and Jquery ajax for testing purposes. I'm quite new with WCF. Anyways, I have a service is called "ProductsService" has four parameters that is invoked from Jquery Ajax. I had a little problem with it, but thankfully I resolved it. My solution by estimation, so can any body explain to me why this problem solved this way?

Here the problem scenario.

I inserted new product from Ajax to WCF service method that will store the parameters in SqlParameter . However, only one SqlParameter has a value and the rest of SqlParameter were null. I restructured my method a bit, but still the same. Then I tried to add local variables to see if it would hold the values and store them into SqlParameter .

This is the method

public void insertProdect(int categoryId, string name, string discrption, decimal price)
    {
        // for debuge

        int t1 = categoryId;
        String t2 = name;
        String t3 = discrption;
        decimal t4 = price;


        String sc = ConfigurationManager.ConnectionStrings["BDCS"].ConnectionString;
        using (SqlConnection con = new SqlConnection(sc))
        {

            //
            SqlCommand cmd = new SqlCommand("spInsertNewProductByCategoryId", con);
            cmd.CommandType = CommandType.StoredProcedure;

            //
            SqlParameter CategoryId = new SqlParameter();
            CategoryId.ParameterName = "@CategoryId";
            //CategoryId.Value = categoryId;
            CategoryId.Value = t1;

            //
            SqlParameter ProductName = new SqlParameter();
            ProductName.ParameterName = "@ProductName";
            //ProductName.Value = ProductName;
            ProductName.Value = t2;

            //
            SqlParameter ProductDescription = new SqlParameter();
            ProductDescription.ParameterName = "@ProductDescription";
            //ProductDescription.Value = ProductDescription;
            ProductDescription.Value = t3;

            //
            SqlParameter ProductPrice = new SqlParameter();
            ProductPrice.ParameterName = "@ProductPrice";
            //ProductPrice.Value = price;
            ProductPrice.Value = t4; 

            //
            cmd.Parameters.Add(CategoryId);
            cmd.Parameters.Add(ProductName);
            cmd.Parameters.Add(ProductDescription);
            cmd.Parameters.Add(ProductPrice);

            //
            con.Open(); 
            cmd.ExecuteNonQuery();

        }

ajax call

     $(document).on("click", "#doInsertNewProduct", function () {

    $.when(
        $.ajax({
            url: "../ProductsService.svc/insertProdect",
            method: "post",
            contentType: "application/json; charset=utf-8",

            data: JSON.stringify({
                categoryId: $("#InsertCatogeryTextName").val(),
                name: $("#InsertProductTextName").val(),
                discrption: $("#InsertProductTextDiscrption").val(),
                price: $("#InsertProductTextPrice").val()
            }),
            success: function () {
                location.reload();
                console.log("Done! Successfully insert new Product");
            },
            error: function () {
                console.log("Error! unbale to insert new Product");
            }
        }));

});

Thanks all

Answer 1

You don't need local variables for this - either for the individual SqlParameter s or the values. Your code would be simpler as:

public void InsertProduct(int categoryId, string name, string description, decimal price)
{
    String sc = ConfigurationManager.ConnectionStrings["BDCS"].ConnectionString;
    using (SqlConnection con = new SqlConnection(sc))
    {
        con.Open(); 
        using (SqlCommand cmd = new SqlCommand("spInsertNewProductByCategoryId", con))
        {
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.Add("@CategoryId").Value = categoryId;
            cmd.Parameters.Add("@ProductName").Value = name;
            cmd.Parameters.Add("@ProductDescription").Value = description;
            cmd.Parameters.Add("@ProductPrice").Value = price;
            cmd.ExecuteNonQuery();
        }
    }
}

I'd strongly advise you to specify the types of the parameters as well, mind you, eg

cmd.Parameters.Add("@CategoryId", SqlDbType.Int).Value = categoryId;