LINQ语句生成的查询与LinqPad不同

Question

I have the following code that queries some data via a LEFT JOIN:

Model1 db = new Model1();

db.Database.Log = System.Console.Write;

var x = from e in db.Employees
        where e.id == 746
        join f in db.Company on e.CompanyID equals f.ID into fa
        from fr in fa.DefaultIfEmpty()
        select new
        {
          e.id,
          e.name,
          companyName = fr.name
        };

x.Any(); // to see the query in console

The classes used here are generated by Visual Studio Wizards to make sure that the model and DB context code is correct.

When i run that code in LINQpad the SQL query looks like

SELECT [t0].[id] AS [id], [t0].[name] AS [name], [t1].[name] AS [companyName]
FROM [Employees] AS [t0]
LEFT OUTER JOIN [Company] AS [t1] ON [t0].[CompanyID] = [t1].[ID]
WHERE [t0].[id] = 1615

But when i run the code in a simple Console Application i get the following cryptic query that is totally wrong:

SELECT 
    CASE WHEN ( EXISTS (SELECT 
        1 AS [C1]
        FROM  [dbo].[Employees] AS [Extent1]
        LEFT OUTER JOIN [dbo].[Company] AS [Extent2] ON ([Extent1].[CompanyID] = [Extent2].[ID]) OR (([Extent1].[CompanyID] IS NULL) AND ([Extent2].[ID] IS NULL))
        WHERE 1615 = [Extent1].[id]
    )) THEN cast(1 as bit) ELSE cast(0 as bit) END AS [C1]
    FROM  ( SELECT 1 AS X ) AS [SingleRowTable1]

I tried to find a solution for hours now and LINQ just doesnt get the query right.

Did anybody have the same issue and solved it somehow? Any help is much appreciated.

Answer 1

This query looks correct to me. The LINQpad query looks different, because in your code you use Any() .

Try the following query in LINQpad. It should show the same sql:

 (from e in Employees
    where e.id == 746
    join f in Company on e.CompanyID equals f.ID into fa
    from fr in fa.DefaultIfEmpty()
    select new
    {
      e.id,
      e.name,
      companyName = fr.name
    }).Any()

To see the correct query in your console, you could use ToList() instead of Any()

Answer 2

Obviously the two are using different underlying providers. LinqPAD is treating x and x.Any() as two separate queries - it executes x in SQL and executes x.Any() in-memory.

Either the compiler or the provider your console app uses creates one IQueryable , so you end up with one SQL query. Note that you should be getting the right answer , but the combined SQL query removes items that are not necessary for Any like the field names you request.

If you did other things with x like convert it to a List or called AsEnumerable I'd bet you'd see roughly the same query from the console app.