Linq Left join, where, group by, count()

Question

I need help with doing a Left join in a linq statement. My T-sql query works as expected but I can't seem to get the wanted results from the Linq. I also realize that there are ton of questions like mine, but I can't seem to apply any of the solutions to my case.

Products table

+---+------------+-----------+
|   |transportID |  Type(int)|
+---+------------+-----------+
| 1 | 5          | 1         |
| 2 | 5          | 3         |
| 3 | 6          | 3         |
+---+------------+-----------+

Stores

+---+------------+-------------+
|   |Name        |Type1(string)|
+---+------------+-------------+
| 1 | Ho         | 1           |
| 2 | He         | 2           |
| 3 | Be         | 3           |
| 4 | Ke         | 4           |
| 5 | Fe         | 5           |
+---+------------+-------------+

My wanted result is

+---+------------+-------------+
|   |Type        |Count        |
+---+------------+-------------+
| 1 | 1          | 1           |
| 2 | 2          | 0           |
| 3 | 3          | 1           |
| 4 | 4          | 0           |
| 5 | 5          | 0           |
+---+------------+-------------+

My tsql that works as intended

SELECT 
    Type1,
    Count(Pro.transportId) as Count

FROM dbo.stores as sto

left Join dbo.products as pro on (sto.Type1 = pro.Type AND pro.transportId=5)

Where Type1 is not null
  group by Type1
  ORDER BY Type1 * 1 ASC

My Linq attempt returns this.

+---+------------+-------------+
|   |Type        |Count        |
+---+------------+-------------+
| 1 | 1          | 1           |
| 3 | 3          | 1           |
+---+------------+-------------+

Linq Statement.

var res =   (from sto in _context.Stores
                             join pro in _context.Products on sto.Type1 equals System.Data.Objects.SqlClient.SqlFunctions.StringConvert((double)pro.Type).Trim()
                             where pro.transportId == transportId
                             group pro by pro.Type1 into pt1
                             select new TypeTransportation()
                             {
                                 Type = pt1.Key, // Needs to be int
                                 Count = pt1.Count()
                             }).ToList();

I've tried doing some defaultifempty but can't seem to make it work.

Answer 1

Here is MSDN link "How to: Perform Left Outer Joins" with LINQ: https://msdn.microsoft.com/en-gb/library/bb397895.aspx

You code should be like this:

        var res = (from sto in _context.Stores
               join pro in _context.Products on sto.Type1 equals System.Data.Objects.SqlClient.SqlFunctions.StringConvert((double)pro.Type).Trim() into grpJoin
               from product in grpJoin.DefaultIfEmpty()
               where product.transportId == transportId
               group product by product.Type1 into pt1
               select new TypeTransportation()
               {
                   Type = pt1.Key, // Needs to be int
                   Count = pt1.Count()
               }).ToList();

Answer 2

Wow .. lastly i did it ..

      var transportId = 5;
      var res = from s in _context.Stores
                let Type = _context.Stores.Take(1).Select(x => s.Type1).Cast<int>().FirstOrDefault()
                group Type by Type into pt1
                select new TypeTransportation
                {
                    Type = pt1.Key, // Needs to be int
                    Count = _context.Products.Where(i => i.transportId == transportId && i.Type == pt1.Key).Count()
                };            

      foreach (var item in res)
      {
          Console.WriteLine(item.Type + " " + item.Count);
      }

      Console.ReadKey();

Answer 3

I can't do it in query syntax, but using extension method syntax it will be

var products = new[]
{
    new {transportId = 5, Type = 1},
    new {transportId = 5, Type = 3},
    new {transportId = 6, Type = 3},
    new {transportId = 5, Type = 3},
    new {transportId = 5, Type = 5},
};

var stores = new[]
{
    new {Name = "Ho", Type1 = "1"},
    new {Name = "He", Type1 = "2"},
    new {Name = "Be", Type1 = "3"},
    new {Name = "Ke", Type1 = "4"},
    new {Name = "Fe", Type1 = "5"},
};

var transportId = 5;
var res = stores                    
    .GroupJoin(
        inner: products
            .Where(product =>
                product.transportId == transportId),
        innerKeySelector: product => product.Type,
        outerKeySelector: store => Int32.Parse(store.Type1),
        resultSelector: (store, storeProducts) =>
            new
            {
                StoreType = store.Type1,
                StoreName = store.Name,
                ProductsCount = storeProducts.Count()
            })
    .ToList();

foreach (var item in res)
{
    Console.WriteLine(item);
}

Just replace Int32.Parse with appropriate sql function call for actual DbContext query code.

---

With query syntax this is probably the best I can propose:

var res =
    from store in stores
    join product in 
        (from prod in products where prod.transportId == transportId select prod)
        on store.Type1 equals product.Type.ToString() into storeProducts
    select new
    {
        StoreType = store.Type1,
        StoreName = store.Name,
        ProductsCount = storeProducts.Count()
    };