MVC ADO.NET 在插入值时预期参数错误

Question

问题消息：消息“参数化查询 '(@ProductName nvarchar(3),@SupplierID nvarchar(4000),@CategoryID' 需要参数 '@SupplierID'，但未提供。”字符串

我一直在尝试使用 MVC 操作将多个值插入到经典北风表的产品表中。 列出表格时没有任何问题，但是当我尝试使用脚手架创建页面（自动生成）插入值时，它给了我上面的错误。

这是我的 ProductController 和 AddProduct cshtml

控制器

public class ProductController : Controller
    {
        public string connectionString = @"Data Source = DESKTOP-O5J7OII\SQLEXPRESS01; Initial Catalog = NORTHWND; Integrated Security = True";
        //NORTHWNDEntities Kod = new NORTHWNDEntities();
        //Product x = new Product();

        public ActionResult Index(Product t = null)
        {


            DataTable tableProduct = new DataTable();
            using (SqlConnection sqlCon = new SqlConnection(connectionString))
            {
                sqlCon.Open();
                SqlDataAdapter sqlDA = new SqlDataAdapter("use NORTHWND SELECT * FROM Products Order By ProductID ASC", sqlCon);
                sqlDA.Fill(tableProduct);

            }

            return View(tableProduct);


            //var result = Kod.Products.Where(x => x.ProductID > 0).OrderBy(x => x.ProductID).ToList();


            //return View(result.ToList());
        }

        public ActionResult AddProduct()
        {
            return View(new WebApplication1.Product());
        }

        [HttpPost]
        public ActionResult AddProduct(Product productModel)
        {
            using (SqlConnection sqlCon = new SqlConnection(connectionString))
            {
                sqlCon.Open();
                string query = @"INSERT INTO Products VALUES(@ProductName,@SupplierID,@CategoryID,@QuantityPerUnit,@UnitPrice,@UnitsInStock,@UnitsOnOrder,@ReorderLevel)";
                SqlCommand sqlCmd = new SqlCommand(query, sqlCon);
                sqlCmd.Parameters.AddWithValue("@ProductName", productModel.ProductName);
                sqlCmd.Parameters.AddWithValue("@SupplierID", productModel.SupplierID);
                sqlCmd.Parameters.AddWithValue("@CategoryID", productModel.CategoryID);
                sqlCmd.Parameters.AddWithValue("@QuantityPerUnit", productModel.QuantityPerUnit);
                sqlCmd.Parameters.AddWithValue("@UnitPrice", productModel.UnitPrice);
                sqlCmd.Parameters.AddWithValue("@UnitsInStock", productModel.UnitsInStock);
                sqlCmd.Parameters.AddWithValue("@UnitsOnOrder", productModel.UnitsOnOrder);
                sqlCmd.Parameters.AddWithValue("@ReorderLevel", productModel.ReorderLevel);
                sqlCmd.Parameters.AddWithValue("@Discontinued", productModel.Discontinued);
                sqlCmd.ExecuteNonQuery();
            }
            return RedirectToAction("Index");
        }

和 .cshtml

@model WebApplication1.Product

@using (Html.BeginForm()) 
{
    @Html.AntiForgeryToken()

    <div class="form-horizontal">
        <h4>Product</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.ProductName, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.ProductName, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.ProductName, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.QuantityPerUnit, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.QuantityPerUnit, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.QuantityPerUnit, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.UnitPrice, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.UnitPrice, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.UnitPrice, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.LabelFor(model => model.Discontinued, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                <div class="checkbox">
                    @Html.EditorFor(model => model.Discontinued)
                    @Html.ValidationMessageFor(model => model.Discontinued, "", new { @class = "text-danger" })
                </div>
            </div>
        </div>

        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </div>
    </div>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

谢谢你试图帮助和回复！ :)

Answer 1

第一个问题是您提供的参数（9）比您的查询需要（8）更多。 @Discontinued不是必需的。

错误表示未提供@SupplierID 。 这意味着它具有null值。 检查数据库是否该列支持null值。 然后将该行更改如下：

sqlCmd.Parameters.AddWithValue("@SupplierID", productModel.SupplierID ?? DBNull.Value);

?? 是空合并运算符。 建议使用存储过程：

CREATE PROC AddProduct
@ProductName nvarchar(100),
@SupplierID int=null, /*This line inserts a DBNull, if parameter is null*/
@CategoryID int,
@QuantityPerUnit int,
@UnitPrice money,
@UnitsInStock int,
@UnitsOnOrder int,
@ReorderLevel int
BEGIN

INSERT INTO Products VALUES(@ProductName,@SupplierID,@CategoryID,@QuantityPerUnit,@UnitPrice,@UnitsInStock,@UnitsOnOrder,@ReorderLevel)

END