DinkToPdf Net Core not able to load DLL files

Question

I am trying to generate PDFs from HTML SQL server database using DinkToPdf library.

In the startup file I have added:

var context = new CustomAssemblyLoadContext();
context.LoadUnmanagedLibrary(Path.Combine(Directory.GetCurrentDirectory(), "libwkhtmltox.dll"));

The line gives me this error on launching the web app:

DllNotFoundException: Unable to load DLL 'C:\Program Files\IIS Express\libwkhtmltox.dll' or one of its dependencies: The specified module could not be found. (Exception from HRESULT: 0x8007007E)

System.Runtime.Loader.AssemblyLoadContext.InternalLoadUnmanagedDllFromPath(string unmanagedDllPath)

DllNotFoundException: Unable to load DLL 'C:\Program Files\IIS Express\libwkhtmltox.dll' or one of its dependencies: The specified module could not be found. (Exception from HRESULT: 0x8007007E)

Embitter

Is it just okay if you import dinktopdf using nuget? insead of loading it directly as unamange? – Foreshow

Hello, I have imported. I have installed it well. In its description of use, I must import the dll files from the run. But this method Directory.GetCurrentDirectory() seems to not bet working on Asp.Net Core 3.0 – Embitter

Asp.Net Core Directory.GetCurrentDirectory() I think is the culprit here. It is returning C:\Program Files\IIS Express\ as the default folder for the project – Embitter

Farzaneh Talebi posted an Answer saying "I had same problem and this tutorial helped me: medium.com/volosoft/…" – Aras

Answer 1

I found some work-arounds. They are not perfect but worth a try, and they did do help and I was able to generate PDFs from SQl Server. I put the .dll files in the following folder and it worked.

C:\Program Files\IIS Express

and the loaded the .dll files with

Path.Combine(Directory.GetCurrentDirectory(), "libwkhtmltox.dll");

The other way I went for the whole Path

context.LoadUnmanagedLibrary(Path.GetFullPath(@"C:\Users\User\source\repos\WebSolution\WebApp\libwkhtmltox.dll"));

Both of them worked. However, I urge Net Core developers to work on the GetCurrentDir very well. Or a Method to load from the Project or Solution Folder

Path.Combine(Directory.GetCurrentDirectory(), "libwkhtmltox.dll");

Embitter

It does work locally,however when I publish to azure an error occured. – Denitrify

What of mac . ? – Belen

Answer 2

Just in case anyone else is having the same issue I was able to solve it by installing Microsoft Visual C++ 2015 Redistributable.

Reposit

I had a similar issue when loading a legacy 32bit dll in a UAT environment. The C++ 2010 Redistributable worked for this particular dll. – Boorman

Thx Very Much...local was ok but production - other serwer not working - YOU SAVE MY DAY – Cyprinodont

Wow, installing Microsoft Visual C++ 2015 Redistributable works for me, here is the link to this microsoft.com/en-us/download/details.aspx?id=52685 – Erythromycin

@LuqmanCheema We're sorry, this download is no longer available. - now what? – Gouda

Answer 3

It is mentioned in library's git repo that you should download binaries and include them in your source code:

Copy native library to root folder of your project. From there .NET Core loads native library when native method is called with P/Invoke. You can find latest version of native library here. Select appropriate library for your OS and platform (64 or 32 bit).

What was breaking things was that I was going to that url and right click on each file and select save link as(chrome). This leads to a broken file being downloaded:

DON'T DO THAT you have to open each file within github and then use that Download button. The healthy file is much bigger than what you would get if you go the wrong way!

ridiculous but the problem may be caused by this ...

Cittern

I am using this solution, and it's now worked for me. So I just manually download the dll file, even I have libwkhtmltox.dylib and libwkhtmltox.so files. – Benoite

Answer 4

On Asp.Net Core application I use it like this to get the current directory on runtime

#if DEBUG
            //windows
            string filePath = $@"{Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)}\libwkhtmltox.dll";
#else
            //linux
            string filePath = @$"{(($@"{Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location)}/libwkhtmltox.so").Replace(@"\", @"/"))}";
#endif
            CustomAssemblyLoadContext context = new CustomAssemblyLoadContext();
            context.LoadUnmanagedLibrary(filePath);
            serviceCollection.AddSingleton(typeof(IConverter), new SynchronizedConverter(new PdfTools()));
#endregion

Arceliaarceneaux

I would recommend using System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform() instead, check the platform if it's Windows or Linux and set the appropriate path. This way Debug won't be tied to Linux. – Koontz

Also recommending this approach https://mcmap.net/q/134332/-determine-operating-system-in-net-core. Works nice for all platforms – Formalism

Answer 5

if you are using asp.net core on Linux then you need to install required packages by using following command

apt-get update \
&& apt-get install -y --no-install-recommends \
    zlib1g \
    fontconfig \
    libfreetype6 \
    libx11-6 \
    libxext6 \
    libxrender1 \
&& curl -o /usr/lib/libwkhtmltox.so \
    --location \
    https://github.com/rdvojmoc/DinkToPdf/raw/v1.0.8/v0.12.4/64%20bit/libwkhtmltox.so

Majorette

this command need to be used by root permissions, we need to call 'sudo su' command before using this – Majorette

following commands helped when DinkToPdf was not showing images properly sudo apt-get install libgdiplus sudo apt-get install xvfb libfontconfig wkhtmltopdf sudo apt-get install libc6-dev sudo apt-get install openssl sudo apt-get install libssl1.0-dev – Majorette