Search code examples
c#cil.net-reflector

Converting IL to C# with no syntactic sugar

I'm looking for a program that will show me the lowest level (ie. no syntactic sugar) C# code given IL code.

I tried using .NET Reflector to view a .exe file that contained a simple console app with a foreach loop, hoping to see GetEnumerator(), MoveNext(), Current etc, however it showed it as a foreach loop.

Does such a program exist? Or is it possible to select "no syntactic sugar" in .NET Reflector?

Solution

  • Current versions of ILSpy have a sizable set of options for enabling/disabling decompiler transformation features:

    ...
        static void Main(string[] args) {
            foreach (var arg in args) {
                Console.WriteLine(arg);
            }
        }
...

    enter image description here If needed, you could go further than this by stripping out logic in ICSharpCode.Decompiler.IL.Transforms.* and ICSharpCode.Decompiler.CSharp.StatementBuilder; Perhaps open an issue asking, whether a PR for your changes would be appreciated, as most of these "rawness" settings have been added relatively recently.

    A better example with enumerators

    A laconic snippet of code

    var numbers = new List<int> { 0, 1, 2 };
foreach (var num in numbers) Console.WriteLine(num);

    compiles to 

    System.Collections.Generic.List<int> list = new System.Collections.Generic.List<int>();
list.Add(0);
list.Add(1);
list.Add(2);
System.Collections.Generic.List<int> numbers = list;
System.Collections.Generic.List<int>.Enumerator enumerator = numbers.GetEnumerator();
try
{
    while (enumerator.MoveNext())
    {
        int num = enumerator.Current;
        System.Console.WriteLine(num);
    }
}
finally
{
    ((System.IDisposable)enumerator).Dispose();
}

    (as seen with all transformation settings disabled)

    Further on for-loops:

    As far as compilation goes, for (a; b; c) d is the same as a; while (b) { d; c; } (save for placement of continue-label), so decompilers will take liberty with deciding what kind of loop it might have been based on context similarity between init-statement, condition, and post-statement, so you might even write code by hand

    var a = 0;
while (a < args.Length) {
    Console.WriteLine(args[a]);
    a++;
}

    that will be detected as a for-loop (for there is no telling in IL)

    for (int a = 0; a < args.Length; a++)
{
    System.Console.WriteLine(args[a]);
}