Is that possible to give DLL path from USB device in dllimport in C# application

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[DllImport("DriveLibrary.dll", CallingConvention = CallingConvention.Cdecl, EntryPoint =_TogglePause)]
public static extern bool _TogglePause(bool b);

public bool TogglePause(bool b)
{
debug("TogglePause");
return _TogglePause(b);
}

What I have tried:

string filepath=Environment.CurrentDirectory + @"\DLL\" + DriveLibrary.dll;

[DllImport(filepath, CallingConvention = CallingConvention.Cdecl, EntryPoint =_TogglePause)]
public static extern bool _TogglePause(bool b);

public bool TogglePause(bool b)
{
debug("TogglePause");
return _TogglePause(b);
}

Posted 14-Apr-16 19:59pm

Member 10958630

Updated 14-Apr-16 20:31pm

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Sergey Alexandrovich Kryukov 15-Apr-16 2:12am

This is possible, but why? It would be something unstable, not working on some other computer. Simple change in number of removable drive would break it. Better don't do it.

—SA

Garth J Lancaster 15-Apr-16 2:20am

:-) I've re-iterated this at the bottom of my reply

Sergey Alexandrovich Kryukov 15-Apr-16 2:30am

Good point!
—SA

Member 10958630 15-Apr-16 2:28am

All I want is to Import Dll From Usb Devices becasue My dll is not same for all the computers.

Sergey Alexandrovich Kryukov 15-Apr-16 2:36am

Bad idea. Very bad. One day your removable drive is "E" and all works, another day it's "F". And you cannot dynamically scan drives, find the "right" one, as the path should be static. Just a waste.

Here is the problem: you have to formulate your ultimate goals. What you do is mixing the problem with your views on how it should be solved; we don't know your ultimate goals and cannot suggest a reasonable alternative...

You did not provide any reasonable motivation. Why, for example you cannot create an installed doing different deployment for different machines? Yes, installer is a bad thing, but not where it is important; and you are falling into the opposite extreme...

—SA

Member 10958630 15-Apr-16 2:47am

because of security reason. if usb Device is connected then My software will run. otherwise not.

Sergey Alexandrovich Kryukov 15-Apr-16 2:54am

You did not explain this reason. If you need to use a USB flash drive as a key, you don't need a DLL there.
Again, everything is reduced to the same thing: you don't share the ultimate goals.
—SA

Member 10958630 15-Apr-16 3:19am

I had Done the key Part.but i want to keep my dll only In Usb Device not anywhere in system.

Sergey Alexandrovich Kryukov 15-Apr-16 8:53am

I already explained what your problem is, and even provided the solution, but major problem is keeping your goals in secret :-)
—SA

Kerito Nation 25-Jan-21 1:26am

if you have any solution just give it. why you asking so much question.

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Garth J Lancaster · Answer 1 · 2016-04-14T20:12:00

in a word, 'no', not as you have tried it it above - there's a defined route that's taken to locate DLL's :-

- starting from the directory the Exe is located in,
- then the system directory,
- windows directory,
- current directory,
- then directories listed in the PATH variable

the one way to short circuit the search route I mention is to use the SetDllDirectory, which means a P/Invoke

C#

[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
static extern bool SetDllDirectory(string lpPathName);

All that being said, some corporates block things being run from USB drives, for security reasons

[edit] I'd have issues running things from a usb for lots of reasons - I'd want to make sure it was there for a start. Why dont you set Environment.CurrentDirectory 'down' to the DLL directory you indicate and then set it back before your program exits ? [/edit]

[edit2... and as SAK points out, and I'll paraphrase, 'just because you can, doesnt mean you should' [/edit2]

koolprasad2003 · Answer 2 · 2016-04-14T20:31:00

It is possible as it is also a disk space (through it is removable).
But why you want to do that ?

Just a suggestion:
it looks in your code you have use, Environment.CurrentDirectory but do not use it, since it can be changed in a number of ways (shotrtcut settings, etc). Try one of these options instead:

C#

System.IO.Path.GetDirectoryName(Application.ExecutablePath);

or

C#

System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetEntryAssembly().Location);

I have seen Environment.CurrentDirectory changed their path inadvertently if use something like an OpenFileDialog.

Sergey Alexandrovich Kryukov · Answer 3 · 2016-04-14T20:24:00

What you trying to do is doubly wrong.

First of all, a .NET attribute needs static parameters. That said, it has to be hard-coded path name.
Also, this attribute is totally unrelated not only to current directory, but is not directly related to the executable module location.

In my comment to the question, I tried to explain that if you successfully achieve loading a native module from a removable drive, the situation will become even worse than now when you cannot solve this problem. :-)
If your solved the problem, the solution would work only for some certain environment, when, say, the name of the USB device's volume matches what you expected.

The only reasonable use of this attribute is fixed location of the native module to the .NET assembly using it, say, in the same directory. That said, if you should have the module on the USB drive, the assembly should be there, too.

Yes, there is one apparent, more complicated solution. You can have "small" assembly developed for the sole purpose of using some native module and exposing its functions to the managed. It should be in the same volume come with that native module. And using assembly should load this "small" middleman assembly using Reflection.

Yes, this is certainly the solution, an ugly one, but… why? All I can imagine looks totally insane to me. :-)

—SA

Is that possible to give DLL path from USB device in dllimport in C# application

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