Loadlibrary fails for some dlls,works for others

**streppel** · 10-06-2011

Hey all,

i'm currently on making my Bot more Platform and Computer independent(and easier to keep up to date after a patch) with loading dlls myself and using GetProcAddress to get the adresse of methods.
The problem here is that i can load some dlls, but not all i want. I load about 10 dlls all from the same Folder(game folder) without a problem, but when it comes down to the main dlls with the methods i want to use, it returns a 0 so i can't get the offset to the method.
I used Marshal.GetLastWin32Error what returned 126(looked it up and it said that i can't find the module), but as it is in the same Folder as the others and the filename is written correctly, i really don't get why it's not working.

any help on this would be great
streppel

**Bananenbrot** · 10-06-2011

Since you are appearently using C# for your stuff...
I'm pretty sure the CLR does internally uses LoadLibrary/GetProcAddress for implementing the [DllImport] functionality.
Why fiddling around with that yourself? Also try Win32Exception for handling Win32 exceptions.

**Cypher** · 10-07-2011

Could be any number of things. Post your code.

**streppel** · 10-07-2011

Code:

static class NativeMethods
{
[DllImport("kernel32.dll")]
public static extern IntPtr LoadLibrary(string dllToLoad);

[DllImport("kernel32.dll")]
public static extern IntPtr GetProcAddress(IntPtr hModule, string procedureName);


        [DllImport("kernel32.dll")]
        publicstaticexternbool FreeLibrary(IntPtr hModule);
}

and my Method:
public void LoadLibs()
{
      NativeMethods.LoadLibrary(Pathconst + "Filename.dll"); // ofc checked if Pathconst is correct etc etc,everything right here
}

this works like i said,for some dlls, but not for others

EDIT:
ok i did it another way now(using the games GetProcAddress method instead of loading the dlls in my bot and gettings offsets from there etc etc) which works too,but still i'd like to know why it wasn't working with loading the dll directly

**Bananenbrot** · 10-07-2011

Sorry, but I still don't get why you would want to do this.
Decorating your stuff with DllImport is far easier than Load/FreeLibrary it yourself.

If you want to know how to load a dll at a dynamic (= changing) location, try out Reflection.Emit (see Late binding on native DLLs with C# - CodeProject).
There is really no need to use Load/FreeLibrary for that sort of stuff, especially because you might end up doing something wrong (managed people are too lazy).

**streppel** · 10-07-2011

i'm using asm code injection to do my stuff ingame(targeting,casting etc), but for this i have to get the adress at which the methods i want to use are. To get these adresses i wanted to load the library,run getprocaddress on it with the symbol of the method as 2nd argument, and in return, get the offset for the method. then i could simply find the location of the dll in the other process,add the offset and use this adresse for the asm stuff(aka call 0xdeadbeef).
and i didn't want to use static adresses cause this way it's much easier to maintain after patches(symbols tend to stay to same if there was nothing big changed(aka return type,name or arguments), so doing this work once will save me lots of work later

i hope you got it now

**Bananenbrot** · 10-07-2011

Yeah ok... makes sense

**_Mike** · 10-07-2011

Originally Posted by streppel

I used Marshal.GetLastWin32Error what returned 126(looked it up and it said that i can't find the module), but as it is in the same Folder as the others and the filename is written correctly, i really don't get why it's not working.

Iirc you will get that same error if it fails to find all of the DLL's dependencies.