Setting dllimport programmatically in C#

Question

I am using DllImport in my solution.
My problem is that I have two versions of the same DLL one built for 32 bit and another for 64 bit.

They both e

Answer 1

I know this is a really old question (I'm new - is it bad to answer an old question?), but I just had to solve this same problem. I had to dynamically reference a 32-bit or 64-bit DLL based on OS, while my .EXE is compiled for Any CPU.

You can use DLLImport, and you don't need to use LoadLibrary().

I did this by using SetDLLDirectory. Contrary to the name, SetDLLDirectory adds to the DLL search path, and does not replace the entire path. This allowed me to have a DLL with the same name ("TestDLL.dll" for this discussion) in Win32 and Win64 sub-directories, and called appropriately.

public partial class frmTest : Form
{
    static bool Win32 = Marshal.SizeOf(typeof(IntPtr)) == 4;
    private string DLLPath = Win32 ? @"\Win32" : @"\Win64";

    [DllImport("kernel32.dll", SetLastError = true)]
    public static extern bool SetDllDirectory(string lpPathName);
    [DllImport("TestDLL.dll", SetLastError = true)]
    static extern IntPtr CreateTestWindow();

    private void btnTest_Click(object sender, EventArgs e)
    {
        string dllDir = String.Concat(Directory.GetCurrentDirectory(), DLLPath);
        SetDllDirectory(dllDir);

        IntPtr newWindow = CreateTestWindow();
    }
}