How to insert CIL code to C#

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Is it possible to insert IL code to C# method?

I just posted a utility which allows entire C# function bodies to be automatically replaced with inline IL, using a custom attribute. Like similar utilities, this works via the ILDASM/ILASM round-trip which can be set up as a post-build step. The tool also adjusts the PDB in order to preserve single-stepping and setting breakpoints on individual IL instructions in the debugger. It's different from some of the other round-trip IL inliners in that it (only) substitutes for entire function bodies, like this:

    class MyClass
    .locals init ([0] int32 i_arg)
        int MyFunc(int i_arg)
            return 3;

For highly performance-critical methods, I tried using DynamicMethod to improve upon compiler-generated IL, but found that the benefit is lost due to the delegate-calling overhead. Inline IL gives the the beneft of hand-tuned IL without that hit, assuming there are no runtime customizations that you would truly need DynamicMethod for.

The complete source code is located at

How to insert CIL code to C# - c# - csharp, Is it possible to insert IL code to C# method? I just posted a utility which allows entire C# function bodies to be automatically replaced with inline IL, using a  After entering some code and choosing "C# statements" at the top (or "C# Program", whichever suits), click the "IL" button under the code entry area, and you will see the generated IL. Using LINQPad for this is much more convenient than loading up Visual Studio or running the compiler from the command line, then loading up ILDASM and opening the .il file with a text editor.

If inline IL (in the same spirit of inline assembly supported by C and C++ compilers) is what you're looking for, this can be achieved using post-compilation round-trip compiling.

Mike Stall has once written a tool for that, as far as I know it's fairly mature:

Other than that, you could use F# which supports Inline IL.

Writing IL code on Visual Studio, Writing IL straight to C# or VB.NET solution is not supported out-of-box in Visual Studio. To have IL support in our solutions we can use excellent  The ILDASM.EXE loads up any .NET assembly and investigates its contents, including CIL code, manifest and metadata. The ILDASM.EXE is typically capable of dumping all of the metadata from .NET binaries in a CIL opcode representation. Let's double-click the testCalculation method to examine its underlying generated CIL code as in the following:

DynamicMethod is the lightweight way to accomplish this at runtime.

The Microsoft C# compiler doesn't support injection of IL at compile-time, but a code-weaving tool could do so as a post-compile step.

Support embedded il instructions · Issue #927 · dotnet/csharplang , allow writing inline IL code directly inside C# code for example using They would certainly not consider adding something like embedded  How to insert CIL code to C# (4) DynamicMethod is the lightweight way to accomplish this at runtime. The Microsoft C# compiler doesn't support injection of IL at compile-time, but a code-weaving tool could do so as a post-compile step.

The tool you need is called Cecil and is a part of the Mono project.

You can get more information about it here:

Quoted from the website above:

Cecil is a library written by Jb Evain ( to generate and inspect programs and libraries in the ECMA CIL format. It has full support for generics, and support some debugging symbol format.

In simple English, with Cecil, you can load existing managed assemblies, browse all the contained types, modify them on the fly and save back to the disk the modified assembly.

Common Intermediate Language, Common Intermediate Language (CIL), formerly called Microsoft Intermediate Language Please help improve this article by adding citations to reliable sources. Runtimes typically just-in-time compile CIL instructions into native code. Due to standardization of C# and the CLI, the bytecode is now officially known as CIL  Creating your first IL code. After installing the IL Support extension, create a new project and select the Console application with IL Support template from the Templates / Visual C# / IL Support folder. After the project is created, let’s look at these files: Program.cs;

I'll add my own tool to the list of solutions already provided here: InlineIL.Fody.

This uses the Fody assembly weaving tool to modify the assembly at build time. Which means all you have to do is install a NuGet package, add a config file to your project and you're done.

You're then provided with a simple and type-safe API to emit IL instructions, which you can mix with C# code. I believe it's easier to write IL in this way than writing text, and it's also more convenient than ILGenerator since each opcode gets its own method with relevant overloads only.

Here's an example, with using static InlineIL.IL.Emit;:

public static void ZeroInit<T>(ref T value)
    where T : struct

This shows how to access the initblk instruction which C# doesn't currently expose.

Inline IL ASM in C# with Roslyn, Source code for Roslyn changes is available on github Source code of the allows to use a seamlessly integrated inline IL ASM syntax into C#, almost as it was a DSL! Ordinary ) by adding also the case for ( MethodKind. Is there any way to execute an array of IL codes in C# like shell codes in C/C++? I want to create a method, convert it to IL code, obfuscate it and store in an array of bytes and finally want to execute it decrypt the array content and execute IL code.

Write MSIL Code on the Fly with the .NET Framework Profiling API , This article assumes you're familiar with the CLR and C# The need for IL code rewriting emerges when you want to make your changes you can insert the customized prologue and epilogue into the method's IL and give  The window you are looking fro is Debug -> Windows -> Disassembly. You have to be debugging something for it to be present, and while the debugger is attached you can press Ctrl + Alt + D to get to it. You cannot view the assembly code (machine code) at any other time, because it doesn't exist.

Understanding Common Intermediate Language (CIL), The tokens like IL_000, IL_001 etc are called CIL Code labels. The process of adding the item to the stack is called Push and the removing To understand evaluation stack let us see the below C# code using ILDASM.exe. I need to convert the IL to c# code. I have an assembly and I am reading this assembly. I get MethodBody from MethodInfo and the methodbody has a method GetILAsByteArraY() which returns a byte array now I want to convert this IL to C# code. Please help me out in solving this.

Adding a new Bytecode Instruction to the CLR · Performance is a , So let me introduce the matt IL instruction, that you can use like so: ldarg.0 ldarg.1 matt // yay, my name as an IL op-code!!!! ret } in a C# program, see Adding Matt operator to Roslyn  The Microsoft Intermediate Language (MSIL), also known as the Common Intermediate Language (CIL) is a set of instructions that are platform independent and are generated by the language-specific compiler from the source code. The MSIL is platform independent and consequently, it can be executed on any of the Common Language Infrastructure

  • Didn't find any ILFunc attribute in your lib.
  • @Denis I don't think I was providing a lib. It's source code, and there are two files on the web page. The second one (scroll down beyond the additional text) contains the definition for the ILFunc Attribute itself.