轉換T-SQL查詢到LINQ

Question

我想翻譯的查詢是：

SELECT 
    Products.id, [Products].Name 
FROM 
    [Products] 
LEFT JOIN 
    [AvailableProducts] ON [AvailableProducts].IdProduct = [Products].Id 
         AND [AvailableProducts].IdUser = 'daa8ee71-f1d7-4b41-aa1c-464ae730dd63' 
WHERE 
    ([AvailableProducts].IdProduct IS NULL) 

我試圖解決這個問題，這樣的Linq代碼：

public void DataBindGriedProducts(string idUser) 
{ 
    List<Product> data = new List<Product>(); 

    var con = from test in db.AvailableProducts 
       join product in db.Products on new { test.IdProduct, test.IdUser} equals new { product.Id, idUser} 
       select new 
         { 
          surname = product.Name, 
         }; 

    grdConnectedProduct.DataSource = data; 
    grdConnectedProduct.DataBind(); 
} 

但它不是正確。請幫幫我！

Answer 1

我固定它：

var o = (from p in db.Products 
       join p2 in db.AvailableProducts on new { f1 = (int)p.Id, f2 = idUser } equals new { f1 = (int)p2.IdProduct, f2 = p2.IdUser } 

       into temp 
       from x in temp.DefaultIfEmpty() 
       where x.IdProduct == null 
       select new { f1 = p.Name}); 

Answer 2

public void DataBindGriedProducts(string idUser) 
     { 
      List<Product> data = new List<Product>(); 


      var con = from product in db.Products 
       join ap in db.AvailableProducts on new { x= (int)product.Id, y = product.idUser } equals new { x = (int)ap.IdProduct, y = ap.IdUser } 

         where product.IdProduct=null 
         select new 
         { 
          surname = product.Name, 
         }; 

      grdConnectedProduct.DataSource = data; 
      grdConnectedProduct.DataBind(); 
     } 

，並使用lambda表達式。 我想下面的代碼應該工作

public void DataBindGriedProducts(string idUser) 
        { 
         List<Product> data = new List<Product>(); 


         var con = db.Products.Join(db.AvailableProducts, 
            product=>new{(int)product.Id,product.idUser}, 
            ap=> new {(int)ap.IdProduct, ap.IdUser}, 
            (product,ap)=>product) 
            .Where(product=>product.IdProduct=null) 
            .Select(x=>x new 
            { 
             surname = x.Name, 
            }).ToList(); 

         grdConnectedProduct.DataSource = data; 
         grdConnectedProduct.DataBind(); 
        } 

Answer 3

你的T-SQL查詢等於該查詢：

SELECT 
    [product].[Id], 
    [product].[Name] 
FROM 
    [Products] [product] 
     LEFT JOIN (
      SELECT 
       [j].[IdProduct], 
       [j].[IdUser] 
      FROM 
       [AvailableProducts] [j] 
      WHERE 
       [j].[IdUser] = N'daa8ee71-f1d7-4b41-aa1c-464ae730dd63' 
     ) [t1] ON [product].[Id] = [t1].[IdProduct] 
WHERE 
    [t1].[IdProduct] IS NULL AND [t1].[IdUser] IS NULL 

和LINQ查詢有這樣的觀點：

var availableProductsQuery = from ap in db.AvailableProducts 
              where ap.IdUser == "daa8ee71-f1d7-4b41-aa1c-464ae730dd63" 
              select ap; 

       var con = from product in db.Products.AsQueryable() 
          join test in availableProductsQuery 
          on product.Id equals test.IdProduct into j 
          from ap in j.DefaultIfEmpty() 
          where ap == null 
          select product;