Converting C# Anonymous Functions to SQL Where Clauses using Expression Trees

C# Anonymous functions are awesome, they allow you to abstract your code in a beautiful and clean synax.
But trying to integrate this with reflection and generics might get a little bit hard, I had a problem a few days ago... Generate a SQL WHERE clause based on a function, which takes an object of ta generic ype T, and returns a boolean (f(x: T): Boolean).

The function itself will be pretty simple most of the time, the concrete example of the method I was trying to accomplish is the following: db.Update<MyType>(myObj, (o => o.Id == 1))

So basically, that will update the conveniently named table MyType, with myObj data, WHERE Id = 1

So how take an anonymouse function, parse it, and return a string? I knew it was possible, because LINQ does this for SQL, so there must be a way. The first thing I did was search on StackOverflow, which lead me to this good article on Expression Trees.

After learning a bit about that, I knew I had to use Expression Trees, but I still didn't quite understand how, I wanted to use a function on my method, not a Expression Tree, and there is no way to get an Expression Tree from a function, so I asked on StackOverflow, the answer was pretty simple, just use a function on your method call, and in your Update method use a ExpressionTree as argument type.

public bool Update<T>(T obj, Expression<Func<T, bool>> predicate)

That was I can call my function like this Update<MyType>(obj, (t => t.Id == 1))

That was a huge step, now I could work on the Expression Tree itself, I ended up with a quite nice function to get a string based on a Expression Tree, it assumes the body it's just a list of conditions, for example A && (B || C), which is what you'll most likely have to cope with.

Here is the code I used to get a string from my expression, also note the GetValue method is a helper method, used to get the value of a MemberExpression (Thanks again, StackOverflow!)