where can I find a LinQ parser

I'd like to allow my users to write and execute linq queries. For this, I need a linq parser. This parser would understan开发者_如何学Cd only linq expression, not the full C# language.

So, for example, if we have class Order { public int OrderId; } List list = ...

the user should be able to enter in the UI "select p in list where p.OrderId > 2"; And this would return the orders where orderId > 2.

Does it exist?

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The quickest way to do it is to:

1. Embed the expression into an C# file that will generate a method that will return the query as Expression>; e.g., for

   from x in Foos select x.Y
   

   You might emit:

   class Wrapper {
       IEnumerable<blah> Foos;
       public static Expression<Func<object>> Expr { 
           get { return from x in Foos select x.Y; } 
       }
   }
   

2. Invoke the C# compiler on the file.

3. Load the resulting assembly.
4. Access the property
5. Use the Linq tree to your heart's content.

As a byproduct you get type checking and a bunch of other things. The only real downside is you need a good understanding of the environment in which the query will be executing; if one of the things you're trying to do is to understand the environment, then this doesn't help you very much.

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You can create your own Linq providers, here's a walk through on MSDN