a question of using PredicateExtensions create sqlscriptes

here is my logic code:

var predicate = PredicateExtensions.False<Customer>();
predicate = predicate.Or(p => p.CustomerID.Contains("N"));

using (Entities e = new Entities())
{
    var r = from p in e.Customer.AsQueryable().Where(predicate.Compile())
            select p;
开发者_StackOverflow社区    foreach (var _r in r)
        Console.WriteLine(_r.CustomerID);
}

and then i use sql server profiler get the sql scripts like this:

SELECT 
[Extent1].[CustomerID] AS [CustomerID], 
[Extent1].[Custname] AS [CustEname], 
[Extent1].[Site] AS [DefaultSite], 
[Extent1].[Currency] AS [Currency], 
[Extent1].[PayTerm] AS [PayTerm], 
[Extent1].[BAddr1] AS [BillAddr1], 
[Extent1].[BAddr2] AS [BillAddr2], 
[Extent1].[BAddr3] AS [BillAddr3], 
[Extent1].[BContact] AS [BillContact], 
[Extent1].[BTel] AS [BillTel], 
[Extent1].[BFax] AS [BillFax], 
[Extent1].[BEMail] AS [BillEMail], 
[Extent1].[Company] AS [DlvyCompany], 
[Extent1].[Addr1] AS [DlvyAddr1], 
[Extent1].[Addr2] AS [DlvyAddr2], 
[Extent1].[Addr3] AS [DlvyAddr3], 
[Extent1].[Contact] AS [DlvyContact], 
[Extent1].[Tel] AS [DlvyTel], 
[Extent1].[Fax] AS [DlvyFax], 
[Extent1].[EMail] AS [DlvyEMail], 
[Extent1].[Remark] AS [Remark], 
[Extent1].[User] AS [User], 
[Extent1].[DT] AS [UpdateDT]
FROM [dbo].[Customer] AS [Extent1]

that i get all the data from my database, but i hope there is a condition at the end of the sql scripts, means get all the data but customeid contains N(p => p.CustomerID.Contains("N"))

where i get some wrong.... pls give some points.thans!!!

The problem lies in the Compile() method. The IQueryable<T> extension methods that you want to use require expressions as their arguments. Calling AsQueryable() doesn't do anything in your case and the IEnumerable<Customer> extension method Where(Func<Customer, bool>) gets called. What you want to do is to call the IQueryable<Customer> extension method Where(Expression<Func<Customer, bool>>) instead. To do that is simple: just don't call Compile(), predicate is already an expression. Also, the way you use the query expression (from …) doesn't do (almost) anything, so you can leave it out:

var r = e.Customer.Where(predicate);