SQL query slow when executed with LINQ (using full text search) - linq-to-sql

Question

I have a query that's generated by LINQ and generates a time out error.
But when I run the generated query in SQL server management studio it executes in less than one second.
Here's the query:
exec sp_executesql N'SELECT COUNT(*) AS [value]
FROM [dbo].[Document] AS [t0]
INNER JOIN [dbo].[Document_Search_order_nummer](#p0) AS [t1] ON [t0].[DocumentID] = [t1].[Key]
LEFT OUTER JOIN [dbo].[DocType] AS [t2] ON [t2].[Id] = [t0].[DocumentTypeIDOut]
LEFT OUTER JOIN [dbo].[DocTypeFormat] AS [t3] ON [t3].[Id] = [t2].[FormatId]
LEFT OUTER JOIN [dbo].[DocTypeType] AS [t4] ON [t4].[Id] = [t2].[TypeId]
INNER JOIN [dbo].[OriginalDocument] AS [t5] ON [t5].[OriginalDocID] = [t0].[OriginalDocID]
INNER JOIN [dbo].[User] AS [t6] ON [t6].[User_ID] = [t0].[DocumentFrom]
INNER JOIN [dbo].[User] AS [t7] ON [t7].[User_ID] = [t0].[DocumentTo]
WHERE ([t0].[DocumentID] <> #p1)',N'#p0 nvarchar(4000),#p1 int',#p0=N'"*[phone]+*" ',#p1=270675
Below is the log from SQL server profiler:
Using LINQ:
Eventclass= RPC:Completed
ApplicationName= .Net SqlClient Data Provider
CPU= 12625
Reads= 1137844
Writes = 0
Duration = 29989
Using SQL Server Management Studio:
Eventclass= SQL:BatchCompleted
ApplicationName= Microsoft SQL Server Management Studio - Query
CPU= 78
Reads= 31645
Writes = 0
Duration = 99
What's the cause of this big performance difference with an equal query and how can I solve this issue?

Answer 1

We had exactly the same problem once.
One possible cause could be the parameters type mismatching that causes this.
But, this wasn't the issue in our case. Turned out that in some cases the query just takes longer time to execute. So we isolated the query and ran it trough ADO.NET SqlCommand class. Believe it or not when we added extra white spaces between the sql commands caused the query to execute much faster.
So we took the query and created a view from it. It solved our problem.