Single does top(2)

Question

Kind of intresting to see that when i do single, EF used top(2) in the sql query. Anyone know why?

var

 

 

customer = db.Customers.Single(c => c.CustomerID == "ALFKI");

SELECT TOP (2)

[Extent1].[Address] AS [Address],

[Extent1].[City] AS [City],

[Extent1].[CompanyName] AS [CompanyName],

[Extent1].[ContactName] AS [ContactName],

[Extent1].[ContactTitle] AS [ContactTitle],

[Extent1].[Country] AS [Country],

[Extent1].[CustomerID] AS [CustomerID],

[Extent1].[Fax] AS [Fax],

[Extent1].[Phone] AS [Phone],

[Extent1].[PostalCode] AS [PostalCode],

[Extent1].[Region] AS [Region]

FROM [dbo].[Customers] AS [Extent1]

WHERE N'ALFKI' = [Extent1].[CustomerID]

Zeeshan Hirani

Answer 1

Hi zeeshan.
It's the only way to throw an exception if there are more than one result.
If you only want the first, use First instead of Single.

Answer 2

We need the first result and to know if there were more. I figured top 2 would be a little more efficient than streaming the whole set and aborting early which us what LINQ to SQL does :)

[)amien