LINQ to SQL null Query

LINQ to SQL null Query

 

More than once in the Forum, some netizens asked questions about the query of LINQ null. Here we take the Microsoft northwind database as an example to summarize:

For example, how can I implement an SQL statement such as query using LINQ?

SELECT *FROM [Orders] AS [t0]WHERE ([t0].[ShippedDate]) IS NULL

 

VMethod 1:

from o in Orderswhere o.ShippedDate==nullselect o

The corresponding Lamda expression is:

Orders   .Where (o => (o.ShippedDate == (DateTime?)null))

The corresponding SQL statement is:

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]FROM [Orders] AS [t0]WHERE [t0].[ShippedDate] IS NULL

 

VMethod 2:

from o in Orderswhere Nullable<DateTime>.Equals(o.ShippedDate,null)select o

The corresponding Lamda expression is:

Orders   .Where (o => Object.Equals (o.ShippedDate, null))

The corresponding SQL statement is:

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]FROM [Orders] AS [t0]WHERE [t0].[ShippedDate] IS NULL

 

VMethod 3:

from o in Orderswhere !o.ShippedDate.HasValueselect o

The corresponding Lamda expression is:

Orders   .Where (o => !(o.ShippedDate.HasValue))

The corresponding SQL statement is:

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]FROM [Orders] AS [t0]WHERE NOT ([t0].[ShippedDate] IS NOT NULL)

 

VMethod 4:

from o in Orderswhere o.ShippedDate.Value==(DateTime?)nullselect o

The corresponding Lamda expression is:

Orders   .Where (o => ((DateTime?)(o.ShippedDate.Value) == (DateTime?)null))

The corresponding SQL statement is:

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]FROM [Orders] AS [t0]WHERE ([t0].[ShippedDate]) IS NULL

 

VMethod 5:

from o in Orderswhere  System.Data.Linq.SqlClient.SqlMethods.Equals(o.ShippedDate.Value,null)select o

The corresponding Lamda expression is:

Orders    .Where (o => Object.Equals (o.ShippedDate.Value, null))

The corresponding SQL statement is:

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]FROM [Orders] AS [t0]WHERE ([t0].[ShippedDate]) IS NULL

The above methods are only implemented in the LINQ to SQL validation, and the LINQ to EF is not verified.