Question

I am using latest version of Mono.cecil
What I am trying to do is I am having Custom Attributes in a seperate dll and I want to add the attributes to every method in the sample.exe using mono.cecil
but i am getting the error

“Error ‘System.Void Mono.Cecil.AssemblyDefinition::.ctor()’ is declared in another module and needs to be imported”

Can any one help me in resolving it?

Expecting your help…..

     //Main File Sample.exe

class SampleItems
  {

  public static void Main()
  {
  }
    public void Sample()
    {
      Console.WriteLine("sample");
    }

    public void Sample1()
    {
    Console .WriteLine ("sample1");
    }
  }

================================

Seperate application applying the custom attribute

static void Main(string[] args)
    {
      //opens the assembly
      AssemblyDefinition assemblyDefinition = AssemblyDefinition.ReadAssembly(@"E:\MONOCECIL\POC SAMPLES\Sample.exe.exe");

      //AssemblyDefinition as1= AssemblyDefinition .ReadAssembly (@"E:\MONOCECIL\POC SAMPLES\MonoStart\MonoStart\bin\Debug\SampleDll.dll");

      var resolver = new DefaultAssemblyResolver();
      var systemName = AssemblyNameReference.Parse("SampleDll");

      AssemblyDefinition as1 = resolver.Resolve(systemName);

      var ty = assemblyDefinition.MainModule.Import(as1.GetType ());

      var attCtor = ty.Resolve().Methods.First(x => x.Name == ".ctor"
   && x.Parameters.Count == 0); 


foreach (var modDef in assemblyDefinition.Modules)
      {

        foreach (var typeDef in modDef.Types)
        {
          Console.WriteLine("   +--Type {0}", typeDef.Name);

          //All methods in this type  
          foreach (var methodDef in typeDef.Methods)
          {
            var custatt = new CustomAttribute(attCtor);
           methodDef.CustomAttributes.Add(custatt); 

            Console.WriteLine("      --Method {0}", methodDef.Name);
          }


        }
      }

      assemblyDefinition.Write(@"E:\POSTSHARP SAMPLES\ASPECTDNG\Debug\Sampleupdate.exe");
      Console .ReadLine ();
    }  

===============================
Sample dll

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SampleDll
{
 [System.AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple=false )]
  public sealed  class SampleClass :Attribute 

  {

  public SampleClass ()
  {
  }


  }
}

Answer 1

The issue is that the lines:

 var ty = assemblyDefinition.MainModule.Import(as1.GetType ());
 var attCtor = ty.Resolve().Methods.First(x => x.Name == ".ctor" && x.Parameters.Count == 0); 

make absolutely no sense.

Let say you have:

var sampleDll = AssemblyDefinition.ReadAssembly ("SampleDll.dll");
var targetExe = AssemblyDefiniion.ReadAssembly ("SampleExe.exe");

And that you want to add [SampleClass] on each types in SampleExe.exe.

You need to create a reference from the SampleClass type in sampleDll into targetExe

var sampleClass = sampleDll.MainModule.GetType ("SampleClass");
var sampleClassCtor = sampleClass.Methods.First(m => m.IsConstructor);

var ctorReference = targetExe.MainModule.Import (sampleClassCtor);

foreach (var type in targetExe.MainModule.Types) 
    type.CustomAttributes.Add (new CustomAttribute (ctorReference));