无法将类型系统linq IQueryable隐式转换为系统集合的通用列表 [英] Cannot implicitly convert type system linq IQueryable to system collections generic List
问题描述
无法从View Model Controller到View获取数据，我已经在LINQpad中正确检查了查询的工作情况.但是，我缺少可以在View中显示的查询输出的转换.
Unable to fetch Data from View Model Controller to View,i have properly checked the working of query in LINQpad. However I am missing the conversion of the output of query which can be displayable in View.
我有三个数据模型产品，图像，规范，它们仅通过选定的属性组合到ViewModel中，并希望显示它们.
I have three Data Models Products,Images,Specifications which i combined into ViewModel with only selected properties and want to displaythe same.
public class ViewModelController : Controller
{
private OMSEntities db = new OMSEntities();
// GET: ViewModel
public ActionResult Index()
{
var product = new Product();
var prices = new Price();
var orders = new Order();
ProductRegistrationViewModelVM vm = new ProductRegistrationViewModelVM();
vm =(from p in db.Products
join i in db.Images on p.ProductId equals i.Product_Id
join s in db.Specifications on p.ProductId equals s.Product_Id
select new
{
//Product
p.Name,
p.Produt_Code,
p.Description,
//Image
i.Image_Description,
i.Image_Name,
i.image1,
//Specifications
s.Sz_Measurement_Unit,
s.Size,
s.Wg_Measurement_Unit,
s.Weight,
s.Price_Set,
s.Price_Sold
});
vm.Add(new ProductRegistrationViewModelVM());
return View(vm.ToList());
}
ViewModel类
ViewModel Class
public class ProductRegistrationViewModelVM
{
//Products
public int ProductId { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public string Produt_Code { get; set; }
public Nullable<int> Supplier_Id { get; set; }
public IEnumerable<Supplier> Supplier { get; set; }
//Image
public string Image_Description { get; set; }
public string Image_Name { get; set; }
public byte[] image1 { get; set; }
//Specifications
public string Sz_Measurement_Unit { get; set; }
public Nullable<decimal> Size { get; set; }
public string Size_Name { get; set; }
public string Wg_Measurement_Unit { get; set; }
public Nullable<decimal> Weight { get; set; }
public Nullable<int> Price_Set { get; set; }
public Nullable<int> Price_Sold { get; set; }
}
注意:我确实调查了相同的错误堆栈溢出中的问题，但是无法弄清楚.
Note: I did look into the same error Questions in stack overflow However was not able to figure it out.
错误CS0266无法隐式转换类型'System.Linq.IQueryable'.<<匿名类型:字符串名称，字符串Produt_Code，字符串说明，字符串Image_Description，字符串Image_Name，byte [] image1，字符串Sz_Measurement_Unit，十进制?大小，字符串Wg_Measurement_Unit，十进制?重量，整数? Price_Set，整数? Price_Sold >>"到"OMS.ViewModels.ProductRegistrationViewModelVM".存在显式转换(您是否缺少演员表?)
Error CS0266 Cannot implicitly convert type 'System.Linq.IQueryable<<anonymous type: string Name, string Produt_Code, string Description, string Image_Description, string Image_Name, byte[] image1, string Sz_Measurement_Unit, decimal? Size, string Wg_Measurement_Unit, decimal? Weight, int? Price_Set, int? Price_Sold>>' to 'OMS.ViewModels.ProductRegistrationViewModelVM'. An explicit conversion exists (are you missing a cast?)
修复:
如下建议，将ProductRegistrationViewModelVM制成List项，并将ViewModel属性绑定到查询属性.
As Suggested Below ProductRegistrationViewModelVM is made as List item and also ViewModel properties were bound to query properties.
public ActionResult Index()
{
var product = new Product();
var prices = new Price();
var orders = new Order();
List<ProductRegistrationViewModelVM> vm = new List<ProductRegistrationViewModelVM>();
vm= (from p in db.Products
join i in db.Images on p.ProductId equals i.Product_Id
join s in db.Specifications on p.ProductId equals s.Product_Id
select new ProductRegistrationViewModelVM()
{
//Product
Name=p.Name,
Produt_Code= p.Produt_Code,
Description = p.Description,
//Image
Image_Description= i.Image_Description,
Image_Name= i.Image_Name,
image1= i.image1,
//Specifications
Sz_Measurement_Unit= s.Sz_Measurement_Unit,
Size= s.Size,
Wg_Measurement_Unit=s.Wg_Measurement_Unit,
Weight=s.Weight,
Price_Set=s.Price_Set,
Price_Sold= s.Price_Sold
}).ToList();
return View(vm);
}
推荐答案
扩展方法.Select将返回IEnumerable<TResult>，但是您试图将它们分配给类型为ProductRegistrationViewModelVM的业务对象，因此这种分配无效，您可以将vm的类型更改为var，或者如果必须将其设置为List，则查询将类似于以下内容:
The extension method .Select will returns a IEnumerable<TResult>, But you are trying to assign them to a business object of type ProductRegistrationViewModelVM such assignment is invalid, either you can change the type of vm to var or you have to make it as List if so the query will be like the following:
List<ProductRegistrationViewModelVM> vm =(from p in db.Products
join i in db.Images on p.ProductId equals i.Product_Id
join s in db.Specifications on p.ProductId equals s.Product_Id
select new ProductRegistrationViewModelVM
{
//Product
p.Name,
p.Produt_Code,
p.Description,
//Image
i.Image_Description,
i.Image_Name,
i.image1,
//Specifications
s.Sz_Measurement_Unit,
s.Size,
s.Wg_Measurement_Unit,
s.Weight,
s.Price_Set,
s.Price_Sold
}).ToList();
现在，您可以轻松地向其添加类型为ProductRegistrationViewModelVM的另一个对象，因为它是相同类型的列表.而且您也应该在回报上做一些小的改变.如下所示:
Now you can easily add another object of type ProductRegistrationViewModelVM to this since it a List of the same type. And you should do a small change in return as well. which will be like the following;
return View(vm); // No ToList is needed here since it is already a list
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