ASP.NET 铁芯返回

Question

I am using Microsoft Northwind example database. I scaffolded the database and everything works besides this code below

I want to make work this logic:

select * from Products
join Suppliers
   on Products.customer_id = Suppliers.customer_id
where Products.customer_id = 1

My way I tried to make this SQL query in LINQ (No errors in VS 2019):

    public async Task<IActionResult> Index()
    {
         var test = await (from ep in _context.Products
                 join e in _context.Suppliers on ep.SupplierId equals e.SupplierId
                 where (e.SupplierId == 1)
                 select new
                 {ep.ProductName,e.CompanyName}).ToListAsync();
    }
    return View(test);

ERROR after starting the project and going to the Index:

InvalidOperationException: The model item passed into the ViewDataDictionary is of type 'System.Collections.Generic.List 1[<>f__AnonymousType1 1[System.String]]', but this ViewDataDictionary instance requires a model item of type 'System.Collections.Generic.IEnumerable`1[DbFirst.Models.Northwind.Products]'.

Just in case, I am saying that this code works well but it's not what I need:

public async Task<IActionResult> Index()
{
    var test = await _context.Products.Where(x => x.SupplierId == 1).ToListAsync();

    return View(test);
}

Answer 1

David is correct.Your View receives IEnumerable<Product> while your action return the list of anonymous type.

You could create a specific ViewModel for your View:

public class ProductViewModel
{
    public string ProductName{ get; set; }
    public string CompanyName{ get; set; }
}

Then,modify action code to return List<ProductViewModel>

public async Task<IActionResult> Index()
{
     var test = await (from ep in _context.Products
             join e in _context.Suppliers on ep.SupplierId equals e.SupplierId
             where (e.SupplierId == 1)

             select new ProductViewModel
             {  
                ep.ProductName,
                e.CompanyName
             }).ToListAsync();
}
return View(test);

Finally,modify @model of Index View:

@model IEnumerable<ProductViewModel>