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ObjC# is a two way bridge to leverage the CLR into the ObjectiveC programming language and expose your ObjectiveC classes to the CLR. ObjC# is currently only support on Mac OS X. There are a few simple rules to remember when translating a CLR method into a ObjC selector:

  • All method names with arguments are appended based on the argument type. That is MyMethod (int a, float b) would become MyMethodWithInt32:Single:
  • The parameterless constructor are mapped to init
  • Constructors with parameters are mapped like methods but prefaced with init (eg; initWithInt32:)

You also need to remember that if your method is returning a primitive type it is returned as a pointer to the result; so if you had:

public int MyMethod () {
  return 1;

Then your objc# code would be:

NSLog (*(int *)[yourinstance MyMethod]);


The beginning of every ObjC# invokation involves initializing the bridge:

Allocate a new instance of the bridge:

ObjCSharpBridge bridge = [ObjCSharpBridge alloc];

Initialize the bridge:

[bridge init];

After you have a working instance of the bridge you need to load the assembly you wish to interact with:

[bridge loadAssembly: "test-library.dll"]

You are now ready to load a class representation of any class in the loaded assembly (or its referenced assemblies).

Class yourClass = [bridge getClass: "YourNameSpace.YourClass"];

If you wanted to call a static method; you do so directly on the class representation:

[yourClass YourStaticMethod];

You now of course need to initialize the class (mapped to the constructor in the CLR):

id instance = [yourClass initWithInt32:-2];

You may now call methods according to the rules stated above.

Make sure you look at the test/ directory in SVN for more examples of different code/call paths.

Versions & Status

ObjC# is currently at v0.1 and only available from SVN. It can successfully represent classes both ways across the bridge. It can also invoke events through the bridge. Marshalling of primitives works.