DllImport, how to check if the DLL is loaded?

Question

I am doing a P/Invoke, and I am using the following method

[DllImport("Authz.dll", SetLastError = true)]
    public static extern BOOL AuthzFreeContext(
        IntPtr phAuthzResourceManager);

even though its working, how is it guaranteed that Authz.dll is always loaded into my code. Suppose my dll is some XXX.dll how should I check in general if that dll is loaded or not before using that, so that I don't get a method not found exception.

You can P/Invoke on loadlibrary and see if that succeeds? http://www.pinvoke.net/default.aspx/kernel32.loadlibrary — rene, Aug 06 '12 at 11:58

score 15 · Accepted Answer · edited Sep 10 '21 at 08:20

15

Marshal.PrelinkAll(Type)

or

Marshal.Prelink(MethodInfo)

Sadly, the documentation fails to mention any exceptions being thrown if the DLL is not found. I have just verified via a simple app that it is indeed a DllNotFoundException being thrown.

edited Sep 10 '21 at 08:20

Wai Ha Lee

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answered Aug 06 '12 at 11:56

leppie

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What does happen if Prelink does fail? According to the docs there is no error code or exception thrown when something could not be resolved. – Alois Kraus Aug 06 '12 at 12:31
@AloisKraus: `DllNotFoundException` IIRC (or some `IOException`). – leppie Aug 06 '12 at 12:55
@AloisKraus: Easy enough to test ;p – leppie Aug 06 '12 at 12:58
1

It can throw EntryPointNotFoundException when method doesn't exist. This can happen for DLL with different version. – May 21 '17 at 23:50
Also, you can get a BadImageFormatException if your try to load a corrupted DLL (happened to me). – Kounavi May 17 '23 at 13:23

DllImport, how to check if the DLL is loaded?

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