c# : DLLImport for a particular dll not working, although an example app shows it working, How can i resolve this?

Question

I am trying to import a dll using relative paths

private const string LzoDll32Bit = @"lib32\lzo_32.dll";

    #region Dll-Imports

    [DllImport(LzoDll32Bit, EntryPoint = "lzo_version_string")]
    private static extern IntPtr lzo_version_string32();
    [DllImport(LzoDll32Bit, EntryPoint = "lzo1x_1_compress", CallingConvention = CallingConvention.Cdecl)]
    private static extern int lzo1x_1_compress32(byte[] src, int src_len, byte[] dst, ref int dst_len, byte[] wrkmem);
    [DllImport(LzoDll32Bit, EntryPoint = "lzo1x_decompress", CallingConvention = CallingConvention.Cdecl)]
    private static extern int lzo1x_decompress32(byte[] src, int src_len, byte[] dst, ref int dst_len, byte[] wrkmem);
    [DllImport(LzoDll32Bit, EntryPoint = "__lzo_init_v2", CallingConvention = CallingConvention.Cdecl)]
    private static extern int __lzo_init_v2_32(uint v, int s1, int s2, int s3, int s4, int s5, int s6, int s7, int s8, int s9);

    #endregion

{"Unable to load DLL 'lib32\\lzo_32.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"}

Now here is the weird thing, http://wallaceturner.com/lzo-for-c , the link for the site where i downloaded a sample project to see how to work with the lzo compressor in c#.net. And when i run the project it successfully works. I see no other dependencies apart from what i have in my project. I am using .Net4.5.2 in both of them.

Here is my full source code for that class

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace TradeAlgo
{
    public class LZOCompressor
    {
        private static TraceSwitch _traceSwitch = new TraceSwitch("Simplicit.Net.Lzo", "Switch for tracing of the LZOCompressor-Class");
        private const string LzoDll32Bit = @"lib32\lzo_32.dll";

        #region Dll-Imports

        [DllImport(LzoDll32Bit, EntryPoint = "lzo_version_string")]
        private static extern IntPtr lzo_version_string32();
        [DllImport(LzoDll32Bit, EntryPoint = "lzo1x_1_compress", CallingConvention = CallingConvention.Cdecl)]
        private static extern int lzo1x_1_compress32(byte[] src, int src_len, byte[] dst, ref int dst_len, byte[] wrkmem);
        [DllImport(LzoDll32Bit, EntryPoint = "lzo1x_decompress", CallingConvention = CallingConvention.Cdecl)]
        private static extern int lzo1x_decompress32(byte[] src, int src_len, byte[] dst, ref int dst_len, byte[] wrkmem);
        [DllImport(LzoDll32Bit, EntryPoint = "__lzo_init_v2", CallingConvention = CallingConvention.Cdecl)]
        private static extern int __lzo_init_v2_32(uint v, int s1, int s2, int s3, int s4, int s5, int s6, int s7, int s8, int s9);

        #endregion

        private byte[] _workMemory = new byte[16384L * 4];

        public LZOCompressor()
        {
            int init = 0;
            init = __lzo_init_v2_32(1, -1, -1, -1, -1, -1, -1, -1, -1, -1);

            if (init != 0)
            {
                throw new Exception("Initialization of LZO-Compressor failed !");
            }
        }

        public byte[] Compress(byte[] src)
        {
            if (_traceSwitch.TraceVerbose)
            {
                Trace.WriteLine(String.Format("LZOCompressor: trying to compress {0}", src.Length));
            }
            byte[] dst = new byte[src.Length + src.Length / 64 + 16 + 3 + 4];
            int outlen = 0;
            lzo1x_1_compress32(src, src.Length, dst, ref outlen, _workMemory);

            if (_traceSwitch.TraceVerbose)
            {
                Trace.WriteLine(String.Format("LZOCompressor: compressed {0} to {1} bytes", src.Length, outlen));
            }
            byte[] ret = new byte[outlen + 4];
            Array.Copy(dst, 0, ret, 0, outlen);
            byte[] outlenarr = BitConverter.GetBytes(src.Length);
            Array.Copy(outlenarr, 0, ret, outlen, 4);
            return ret;
        }

        public byte[] Decompress(byte[] src)
        {
            if (_traceSwitch.TraceVerbose)
            {
                Trace.WriteLine(String.Format("LZOCompressor: trying to decompress {0}", src.Length));
            }
            int origlen = BitConverter.ToInt32(src, src.Length - 4);
            byte[] dst = new byte[origlen];
            int outlen = origlen;
            lzo1x_decompress32(src, src.Length - 4, dst, ref outlen, _workMemory);

            if (_traceSwitch.TraceVerbose)
            {
                Trace.WriteLine(String.Format("LZOCompressor: decompressed {0} to {1} bytes", src.Length, origlen));
            }
            return dst;
        }
    }
}

Please let me know if i am missing any details, would gladly provide anything required. Thanks.

Answer 1

I see the dll's are include in the project, make sure you set the dll's Properties for 'Copy To Output Directory' to 'Copy if newer'. Possibly they are not creating the folders with the dll's in them in your 'Release' folder.