无法在asp.net项目中引用Ghostscript dll

Question

安装Ghostscript之后，如果我尝试在应用程序中添加引用，它就不会出现并给出以下错误， “无法添加对'C：\ Programming File \ gs \ gs9.10 \ gsdll32.dll'的引用。请确保该文件是可访问的，并且它是有效的程序集或COM组件。”

但我继续编写代码并执行，之后它给出了以下错误消息，

“无法在DLL'gsdll32.dll'中找到名为'gsapi_new_instance'的入口点。”

示例代码：

public partial class _Default : System.Web.UI.Page
{
    [DllImport("gsdll32.dll", EntryPoint = "gsapi_new_instance")]
    private static extern int CreateAPIInstance(out IntPtr pinstance,
                                            IntPtr caller_handle);

    [DllImport("gsdll32.dll", EntryPoint = "gsapi_init_with_args")]
    private static extern int InitAPI(IntPtr instance, int argc, IntPtr argv);

    [DllImport("gsdll32.dll", EntryPoint = "gsapi_exit")]
    private static extern int ExitAPI(IntPtr instance);

    [DllImport("gsdll32.dll", EntryPoint = "gsapi_delete_instance")]
    private static extern void DeleteAPIInstance(IntPtr instance);
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    private string[] GetArgs(string inputPath, string outputPath,
                     int firstPage, int lastPage, int width, int height)
    {
        return new[]
{
    // Keep gs from writing information to standard output
    "-q",                     
    "-dQUIET",

    "-dPARANOIDSAFER", // Run this command in safe mode
    "-dBATCH", // Keep gs from going into interactive mode
    "-dNOPAUSE", // Do not prompt and pause for each page
    "-dNOPROMPT", // Disable prompts for user interaction           
    "-dMaxBitmap=500000000", // Set high for better performance

    // Set the starting and ending pages
    String.Format("-dFirstPage={0}", firstPage),
    String.Format("-dLastPage={0}", lastPage),   

    // Configure the output anti-aliasing, resolution, etc
    "-dAlignToPixels=0",
    "-dGridFitTT=0",
    "-sDEVICE=jpeg",
    "-dTextAlphaBits=4",
    "-dGraphicsAlphaBits=4",
    String.Format("-r{0}x{1}", width, height),

    // Set the input and output files
    String.Format("-sOutputFile={0}", outputPath),
    inputPath
};
    }
    public void CallAPI(string[] args)
    {
        var argStrHandles = new GCHandle[args.Length];
        var argPtrs = new IntPtr[args.Length];

        // Create a handle for each of the arguments after 
        // they've been converted to an ANSI null terminated
        // string. Then store the pointers for each of the handles
        for (int i = 0; i < args.Length; i++)
        {
            argStrHandles[i] = GCHandle.Alloc(StringToAnsi(args[i]), GCHandleType.Pinned);
            argPtrs[i] = argStrHandles[i].AddrOfPinnedObject();
        }

        // Get a new handle for the array of argument pointers
        var argPtrsHandle = GCHandle.Alloc(argPtrs, GCHandleType.Pinned);

        // Get a pointer to an instance of the GhostScript API 
        // and run the API with the current arguments
        IntPtr gsInstancePtr;
        CreateAPIInstance(out gsInstancePtr, IntPtr.Zero);
        InitAPI(gsInstancePtr, args.Length, argPtrsHandle.AddrOfPinnedObject());
    }
    private void Cleanup(GCHandle[] argStrHandles, GCHandle argPtrsHandle,
                                   IntPtr gsInstancePtr)
    {
        for (int i = 0; i < argStrHandles.Length; i++)
            argStrHandles[i].Free();

        argPtrsHandle.Free();

        ExitAPI(gsInstancePtr);
        DeleteAPIInstance(gsInstancePtr);
    }
    public void GeneratePageThumbs(string inputPath, string outputPath,
                          int firstPage, int lastPage, int width, int height)
    {
        CallAPI(GetArgs(inputPath, outputPath, firstPage, lastPage, width, height));
    }
    public static byte[] StringToAnsi(string original)
    {
        var strBytes = new byte[original.Length + 1];
        for (int i = 0; i < original.Length; i++)
            strBytes[i] = (byte)original[i];

        strBytes[original.Length] = 0;
        return strBytes;
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        GeneratePageThumbs(@"D:\Hanamantha\Learning\images\Test.pdf", @"D:\Hanamantha\Learning\images", Convert.ToInt32(1), Convert.ToInt32(6), 100, 100);
    }
}