Dllimport work on visual studio but not in iis server

Question

I have a DLL that I have developed. I use this DLL in a website using DllImport.

When I run the website via Visual Studio all is okay, but when I run it with the IIS it is stuck with no errors.

Here's my code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using System.Runtime.InteropServices;
using System.Web.Script.Serialization;
using System.Text.RegularExpressions;

namespace WebApplication1
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        [DllImport("D:\\WebApplication1\\WebApplication1\\bin\\dapreporter.dll", CallingConvention = CallingConvention.StdCall)]
        public static extern IntPtr fndapreporter(string inifile, int nReport, int nYear, int nMonth, int nDay, int nType, int nCode, int precision);

        protected void Page_Load(object sender, EventArgs e)
        {
            try
            {
                string iniFile = File.ReadAllText(@"D:\WebApplication1\WebApplication1\bin\WinDAP.ini");
                
                IntPtr pVariant = fndapreporter(iniFile, 0, 2021, 9, 12, 0, 197, 0);

                object sHtml = Marshal.GetObjectForNativeVariant(pVariant);

                Marshal.FreeCoTaskMem(pVariant);
                pVariant = IntPtr.Zero;
                Response.Write(sHtml.ToString());
            }
            catch(Exception ex)
            {
                Response.Write("ERROR: " + ex.Message);
            }
        }
    }
}

[Please do not upload images of code/errors](https://meta.stackoverflow.com/q/285551) but provide it as text — Klaus Gütter, Dec 12 '21 at 13:40
If that library tries to do printing, then I am not surprised that it works differently under IIS, https://blog.lextudio.com/web-application-differences-in-visual-studio-and-iis-60fec7e311b3 — Lex Li, Dec 12 '21 at 14:44
Make sure your IIS Application Pool is running in 32bit or 64bit to match your .dll. — David Browne - Microsoft, Dec 12 '21 at 15:00
Is the dll x64 bit or x32? Might want to force and test your project as x64 bits - don't use default of any cpu — Albert D. Kallal, Dec 12 '21 at 22:50

Tu deschizi eu inchid · Answer 1 · 2021-12-12T16:18:31.097

A website's files/folders are relative to the home directory for that particular website. Due to the way DllImport works, one can add the desired directory to the PATH environment variable and then specify only the filename.

Try the following:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
using System.Web.Hosting;
using System.Runtime.InteropServices;
using System.Web.Script.Serialization;
using System.Text.RegularExpressions;

namespace WebApplication1
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        [DllImport("dapreporter.dll", CallingConvention = CallingConvention.StdCall)]
        public static extern IntPtr fndapreporter(string inifile, int nReport, int nYear, int nMonth, int nDay, int nType, int nCode, int precision);

        protected void Page_Load(object sender, EventArgs e)
        {
            IntPtr pVariant = IntPtr.Zero;

            try
            {
                //get path to bin directory
                //string binDir = Server.MapPath("~/bin/");
                string binDir = HostingEnvironment.MapPath("~/bin/");

                //add bin directory to PATH so DLLImport can find the DLL
                Environment.SetEnvironmentVariable("PATH", String.Format("{0};{1}", Environment.GetEnvironmentVariable("PATH"), binDir));

                string iniFile = File.ReadAllText(Path.Combine(binDir, "WinDAP.ini"));

                pVariant = fndapreporter(iniFile, 0, 2021, 9, 12, 0, 197, 0);

                object sHtml = Marshal.GetObjectForNativeVariant(pVariant);
                Response.Write(sHtml.ToString());
            }
            catch (Exception ex)
            {
                Response.Write("ERROR: " + ex.Message);
            }
            finally
            {
                if (pVariant != IntPtr.Zero)
                {
                    Marshal.FreeCoTaskMem(pVariant);
                    pVariant = IntPtr.Zero;
                }
            }
        }
    }
}

Resources:

Dllimport work on visual studio but not in iis server

1 Answers1