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Editor to share with you how to use Linq DataLoadOptions, I believe that most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Linq DataLoadOptions restriction

Linq to sql's use of Linq DataLoadOptions is limited, and it only supports one one-to-many relationship. A customer may have multiple orders, and an order may have multiple detailed orders:

DataLoadOptions options = new DataLoadOptions (); options.LoadWith (c = > c.Orders); options.LoadWith (o = > o.Order_Details); ctx.LoadOptions = options; IEnumerable customers = ctx.Customers.ToList ()

The execution of such a statement causes the following SQL to execute N times (with different parameters):

SELECT [t0]. [OrderID], [t0]. [CustomerID], [t0]. [EmployeeID], [t0]. [OrderDate]

[t0]. [RequiredDate], [t0]. [ShippedDate], [t0]. [ShipVia], [t0]. [Freight], [t0].

[ShipName], [t0]. [ShipAddress], [t0]. [ShipCity], [t0]. [ShipRegion], [t0].

[ShipPostalCode], [t0]. [ShipCountry], [t1]. [OrderID] AS [OrderID2], [t1].

[ProductID], [T1]. [UnitPrice], [T1]. [Quantity], [T1]. [Discount], (

SELECT COUNT (*)

FROM [dbo]. [Order Details] AS [t2]

WHERE [T2]. [OrderID] = [t0]. [OrderID]

) AS [count]

FROM [dbo]. [Orders] AS [t0]

LEFT OUTER JOIN [dbo]. [Order Details] AS [T1] ON [T1]. [OrderID] = [t0]. [OrderID]

WHERE [t0]. [CustomerID] = @ x1

ORDER BY [t0]. [OrderID], [t1]. [ProductID]

-- @ x1: Input StringFixedLength (Size = 5; Prec = 0; Scale = 0) [ALFKI]

For many-to-1 relationships, Linq to sql has no restrictions on Linq DataLoadOptions:

DataLoadOptions options = new DataLoadOptions (); options.LoadWith (c = > c.Category); options.LoadWith (c = > c.Order_Details); options.LoadWith (o = > o.Order); ctx.LoadOptions = options; IEnumerable products = ctx.Products.ToList ()

Since multiple products correspond to 1 category and multiple detailed orders correspond to 1 order, only products and detailed orders have a many-to-1 relationship, so there will be only one SQL (however, it is better to do so less, because it consumes too much).

SELECT [t0]. [ProductID], [t0]. [ProductName], [t0]. [SupplierID], [t0].

[CategoryID], [t0]. [QuantityPerUnit], [t0]. [UnitPrice], [t0].

[UnitsInStock], [t0]. [UnitsOnOrder], [t0]. [ReorderLevel], [t0].

[Discontinued], [t3]. [OrderID], [t3]. [ProductID] AS [ProductID2], [t3].

[UnitPrice] AS [UnitPrice2], [t3]. [Quantity], [t3]. [Discount], [t4].

[OrderID] AS [OrderID2], [t4]. [CustomerID], [t4]. [EmployeeID], [t4].

[OrderDate], [t4]. [RequiredDate], [t4]. [ShippedDate], [t4]. [ShipVia]

[t4]. [Freight], [t4]. [ShipName], [t4]. [ShipAddress], [t4]. [ShipCity]

[T4]. [ShipRegion], [T4]. [ShipPostalCode], [T4]. [ShipCountry],

SELECT COUNT (*)

FROM [dbo]. [Order Details] AS [t5]

INNER JOIN [dbo]. [Orders] AS [T6] ON [T6]. [OrderID] = [T5]. [OrderID]

WHERE [T5]. [ProductID] = [t0]. [ProductID]

) AS [count], [T2]. [test], [T2]. [CategoryID] AS [CategoryID2], [T2].

[CategoryName], [t2]. [Description], [t2]. [Picture]

FROM [dbo]. [Products] AS [t0]

LEFT OUTER JOIN (

SELECT 1 AS [test], [t1]. [CategoryID], [t1]. [CategoryName], [t1].

[Description], [t1]. [Picture]

FROM [dbo]. [Categories] AS [t1]

) AS [T2] ON [T2]. [CategoryID] = [t0]. [CategoryID]

LEFT OUTER JOIN ([dbo]. [Order Details] AS [T3]

INNER JOIN [dbo]. [Orders] AS [T4] ON [T4]. [OrderID] = [T3].

[OrderID]) ON [T3]. [ProductID] = [t0]. [ProductID]

ORDER BY [t0]. [ProductID], [t2]. [CategoryID], [t3]. [OrderID]

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