C# retrieve where clause on linq

Question

Is there a way to build a linq query in order to use it later or to display/print it (and more specifically, the where clause) ?

Answer 1

What exactly is it you want? You can capture just the expression from the Where - something like:

Expression<Func<SomeType, bool>> predicate = row => row.IsActive
          && row.Color == "red";

Because this is going to an expression tree, there is a meaningful ToString().

If you want the SQL (etc), then that will be implementation-specific. For example, with LINQ-to-SQL you can use .Log - for example, ctx.Log = Console.Out;

If you want the predicate out of the middle of an IQueryable<T> feed, then that is much trickier...

Answer 2

Isn't LINQ a .NET 3.5-feature?

edit:

http://msdn.microsoft.com/en-us/library/bb332048.aspx

--> LINQ is only available from .NET 3.5, so not 3.0 as the topicstarter asks.

edit2:

Ok, so the TS talks about C# 3.0, which comes with .NET 3.5.

Quite confusing.

Answer 3

You could look at System.Linq.Dynamic its a addon to linq to build dynamic where, orderby etc.

eg tblProduct.Where("product_id = @0", product_id)

That might be of some assistance.

Answer 4

Look at this example from MSDN:

// Lambda expression as executable code.
Func<int, bool> deleg = i => i < 5;
// Invoke the delegate and display the output.
Console.WriteLine("deleg(4) = {0}", deleg(4));

// Lambda expression as data in the form of an expression tree.
System.Linq.Expressions.Expression<Func<int, bool>> expr = i => i < 5;
// Compile the expression tree into executable code.
Func<int, bool> deleg2 = expr.Compile();
// Invoke the method and print the output.
Console.WriteLine("deleg2(4) = {0}", deleg2(4));

Answer 5

Linq cannot be displayed (AFAIK), if you mean 'linq2sql' query (qg. sql query built from linq), no, it cannot be printed out.