LINQ OUTER JOIN查询 - Where子句无效的Null

Question

In my following sample data tables the customer C1 has ordered Vegetables and C2 has ordered Fruits. I want to display name of potential customers C3 and C4 who have not orders yet. So, I use an Outer Join but query always returns the first cutomer C1. It seems, something wrong with my where clause.

Customers table :

CustomerID  CustName
1           C1
2           C2
3           C3
4           C4

Orders table :

OrderID CustomerID  OrderType
1       1           V
2       2           F
3       1           V

LINQ Query to display potential customers with no orders yet:

    public class TestDbController : Controller
    {

       public async Task<IActionResult> TestAction(List<CustomersViewModel> list)
       {
          var Qry = from c in Customers
                     join ord in Orders on c.CustomerId equals ord.CustomerId into c_o
                     from t in c_o.DefaultIfEmpty()
                     where t == null
                     select new  CustomersViewModel() {CustName = c.Name};
          return View(qry.ToList());
        }
    }

UPDATE :

According to @IvanStoev, this seems to be an EF core bug. I should have pointed out that I'm using the following technologies: ASP.NET CORE, EF Core, Visual Studio 2015 - UPDATE 3, and SQL Server Express 2014. I'm including a tag for EF Core in the post.

If someone can find a solution or a workaround, please let me know.

UPDATE 2 :

SQL Server Profiler captures the following following SQL:

exec sp_executesql N'SELECT [c].[CustNumber], @__Empty_0
FROM [Customers] AS [c]
LEFT JOIN [Orders] AS [ord] ON [c].[CustomerID] = [ord].[CustomerID]
ORDER BY [c].[CustomerID]',N'@__Empty_0 nvarchar(4000)',@__Empty_0=N''

But my view is showing only one record. Also, when I place a breakpoint at @for (int t=0; t<Model.Count; t++) in my view shown below, it shows only 1 at the Model.Count :

@model List<MyProject.Models.MyViewModels.CustomersViewModel>

    <form asp-controller="TestDb" asp-action="TestAction" method="post">
    <table class="table">
      <thead>
         <tr>
             <th><label asp-for="@Model.First().CustName"></label></th>
         </tr>
       </thead>
       <tbody>
             @for (int t=0; t<Model.Count; t++)
                {
                  <tr>
                     <td><input type="hidden" asp-for="@Model[t].CustomerId"/ </td>
                     <td><input type="text" asp-for="@Model[t].CustName"/></td>
                  </tr>
                }
       </tbody>
      </table>
      <button type="submit">Save</button>
  </form>

Answer 1

This is actually your query and works (against say Northwind):

var Qry = from c in Customers
              join ord in Orders on c.CustomerID equals ord.CustomerID into c_o
              from t in c_o.DefaultIfEmpty()
              where t == null
              select c;

But simplier way to say that is:

var Qry = from c in Customers
          where !c.Orders.Any()
          select c;