How to easily validate if an input string is valid lambda expression?

Question

For example:

Validate("items.Select(item => item.ToLower())")

will return True, while

Validate("var n=5;")

will return False.

The context is that I want to create an application that allows users to manipulate their data via a lambda expression. If the user inputs a valid lambda expression, the program will execute it. Otherwise, it should fail.

What's the context? How will this be used? Why does it need to be a string version of the LINQ expression and not the LINQ expression? Just trying to arrive at the intent so I can better understand a solution. — Eli Gassert
– Eli Gassert, Commented Nov 16, 2012 at 19:33
FYI that's not a "Linq" expression, it's a Lamba expression. — asawyer
– asawyer, Commented Nov 16, 2012 at 19:34
@zer0ne These are Lambda expressions in a LINQ context. By no means are they restricted to LINQ queries however. — asawyer
– asawyer, Commented Nov 16, 2012 at 19:47

Tomas Grosup · Accepted Answer · 2012-11-16 19:55:24Z

-1

I would recommend of keeping it simple and just trying to execute it. If it isnt valid, it will fail anyway a few milliseconds later.

It also deals with expressions that are syntactically valid, but fail from a different reason.

If you choose to take this approach, than it only takes to use the Dynamic Linq library and you are done.

answered Nov 16, 2012 at 19:55

Tomas Grosup

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3 Comments

asawyer Over a year ago

"it will fail anyway a few milliseconds later" LINQValidate("while(true){var s=\"good luck\"";}");

Tomas Grosup Over a year ago

If he must deal with evil users, he can execute it on a separate thread and kill it if it takes too long.

asawyer Over a year ago

Ok. LINQValidate("System.Diagnostics.Process.Start(\"cmd format c:\");");

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