Simple Examples of joining 2 and 3 table using lambda expression

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情书的邮戳
情书的邮戳 2020-12-25 11:34

Can anyone show me two simple examples of joining 2 and 3 tables using LAMBDA EXPRESSION(
for example using Northwind tables (Orders,CustomerID,EmployeeID)

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  • 2020-12-25 11:48

    try this one to join 2 tables using lambda expression

    var list = dataModel.Customers                     
    .Join( dataModel.Orders, 
          c => c.Id, 
          o => o.CustomerId, 
          (c, o) => new
                     {
                         CustomerId = c.Id, 
                         CustomerFirstName = c.Firstname, 
                        OrderNumber = o.Number
                     });
    
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  • 2020-12-25 11:50

    Code for joining 3 tables is:

    var list = dc.Orders.
                    Join(dc.Order_Details,
                    o => o.OrderID, od => od.OrderID,
                    (o, od) => new
                    {
                        OrderID = o.OrderID,
                        OrderDate = o.OrderDate,
                        ShipName = o.ShipName,
                        Quantity = od.Quantity,
                        UnitPrice = od.UnitPrice,
                        ProductID = od.ProductID
                    }).Join(dc.Products,
                            a => a.ProductID, p => p.ProductID,
                            (a, p) => new
                            {
                                OrderID = a.OrderID,
                                OrderDate = a.OrderDate,
                                ShipName = a.ShipName,
                                Quantity = a.Quantity,
                                UnitPrice = a.UnitPrice,
                                ProductName = p.ProductName
                            });
    

    Thanks

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  • 2020-12-25 12:06
    public void Linq102() 
    { 
    
    string[] categories = new string[]{  
        "Beverages",   
        "Condiments",   
        "Vegetables",   
        "Dairy Products",   
        "Seafood" };  
    
    List<Product> products = GetProductList(); 
    
    var q = 
        from c in categories 
        join p in products on c equals p.Category 
        select new { Category = c, p.ProductName }; 
    
    foreach (var v in q) 
    { 
        Console.WriteLine(v.ProductName + ": " + v.Category);  
    } 
    }
    
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