Viewing the IL code generated from a compiled expression

Question

Is it possible to view the IL code generated when you call Compile() on an Expression tree? Consider this very simple example:

class Program
{
    public int Value { get; set; }

    static void Main(string[] args)
    {
        var param = Expression.Parameter(typeof(Program));
        var con = Expression.Constant(5);
        var prop = Expression.Property(param, typeof(Program).GetProperty("Value"));
        var assign = Expression.Assign(prop, con);
        Action<Program> lambda = Expression.Lambda<Action<Program>>(assign, param).Compile();

        Program p = new Program();
        lambda(p);



        //p.Value = 5;
    }
}

Now, the expression tree does what the last line of Main says. Compile the application, then open it in Reflector. You can see the IL code of p.Value = 5; that does the assignment. But the expression tree was made and compiled at runtime. Is it possible to view the resulting IL code from the compile?

Do you just want the *equivalent* IL for what you are *doing* (i.e. setting a property)? Or is there something about the `Expression` output that you are specifically interested in? — Marc Gravell, Jan 21 '11 at 22:03
Nothing specific. I like looking at the IL code from time to time. But with expressions you can make a method that doesn't get any IL in the compiled assembly. The IL used to *create* that expression tree is there, but not the result of the expression tree's compile itself. Does that make sense? This is simply a curiosity and doesn't serve any real practical purpose that I can see. — , Jan 21 '11 at 22:08
Have you tried with the great **LinqPad** tool ? http://www.linqpad.net/ With it you can display generated code as MSIL and experiment quickly almost anything... — AFract, Jan 21 '11 at 22:48

Eric Lippert · Accepted Answer · 2019-01-22T21:44:19.633

30

Yes! Use this tool:

https://github.com/drewnoakes/il-visualizer

This was incredibly useful when I was implementing and debugging Compile, as I'm sure you can imagine.

edited Jan 22 '19 at 21:44

answered Jan 21 '11 at 22:48

Eric Lippert

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4

Eric, if you have the time, could you flesh this out into a more substantial answer? Link only answers are discouraged on Stack Overflow. – casperOne Sep 16 '12 at 14:10
Too bad it isn't compilable, is there a binary version available? – Jeroen van Langen Oct 09 '13 at 19:31
2

@casperOne: I encourage you to do so. I have nothing to add. – Eric Lippert Oct 09 '13 at 20:14
@JeroenvanLangen: I haven't the faintest idea. I suggest that you address your question to its author. – Eric Lippert Oct 09 '13 at 20:15
@EricLippert: Tyvm for your reaction, I solved this by saving it to an assmebly and using a reflector/ilspy. Tnx again. – Jeroen van Langen Oct 09 '13 at 20:17

score 25 · Answer 2 · edited Aug 14 '11 at 08:00

Create a DynamicAssembly, then a DynamicModule, DynamicType and DynamicMethod. Make that method public and static and pass it to the method CompileTo() on the lambda. When you make the assembly flag it as Save. Then call the Save() method and pass a path. It will be written to disk. Pop it open in reflector.

Something like:

var da = AppDomain.CurrentDomain.DefineDynamicAssembly(
    new AssemblyName("dyn"), // call it whatever you want
    AssemblyBuilderAccess.Save);

var dm = da.DefineDynamicModule("dyn_mod", "dyn.dll");
var dt = dm.DefineType("dyn_type");
var method = dt.DefineMethod(
    "Foo", 
    MethodAttributes.Public | MethodAttributes.Static);

lambda.CompileToMethod(method);
dt.CreateType();

da.Save("dyn.dll");

in case anyone interested in remove the `MethodAttributes.Static` from `DefineMethod` method, there are some research I got http://stackoverflow.com/a/3993023/903505 in conclusion, `CompileToMethod` only works with static method — Ariex, Sep 19 '16 at 00:47

score 0 · Answer 3 · answered Aug 16 '20 at 23:23

0

One of the greatest tools that I have come across online is SharpLab.io and it can do multiple tasks like generating IL, JIT codes, or can verify. It also supports syntax tree.

answered Aug 16 '20 at 23:23

ihimv

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Viewing the IL code generated from a compiled expression

3 Answers3

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