Question

I have two versions of System.Data.SQLite.DLL – for x86 and x64 platform. The x86 version keeps in application folder and x64 version keeps in appFolder\x64 folder.
The application compiled as AnyCPU.
How can i load needed version of SQLite according to windows platform?

Answer 1

If you are using SQLite from http://system.data.sqlite.org, the System.Data.SQLite.DLL is completely managed. There is an underlying native DLL, SQLite.Interop.DLL, that needs to change depending on the process (32- or 64-bit).

I deploy the native libraries in “.\Native\X64” for 64-bit and “.\Native\X86” for 32-bit. At runtime P/Invoke SetDllDirectory to set the DLL load directory pointing at the correct path for the process.
http://msdn.microsoft.com/en-us/library/ms686203(v=vs.85).aspx

(Note that I’m not familiar with the architecture of the legacy System.Data.SQLite.DLL version from http://sqlite.phxsoftware.com)

private static class NativeMethods
{
    [DllImport("kernel32.dll", CallingConvention = CallingConvention.Cdecl)]
    internal static extern bool SetDllDirectory(string pathName);
}

... 

    // Underlying SQLite libraries are native. 
    // Manually set the DLL load path depending on the process.
    var path = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), "Native");
    if(IntPtr.Size == 8) // or: if(Environment.Is64BitProcess) // .NET 4.0
    {
        path = Path.Combine(path, "X64");
    }
    else
    {
        // X32
        path = Path.Combine(path, "X86");
    }
    NativeMethods.SetDllDirectory(path);