Could not load file or assembly 'CefSharp.dll' or one of its dependencies

This is a common error which is caused by not having all required files in the output directory (bin\Debug or bin\Release, depending on which configuration you are running in Visual Studio). CefSharp.dll is a .NET-based DLL which is dependent on other .dll files, which in turn depends further on other .dll and other files.

Here is a listing of the minimum required files:

• libcef.dll (The core Chromium DLL, which basically contains the web browser + the CEF embeddability interface which we depend on)
• icudt.dll (Unicode DLL for Chromium, must also be present)
• CefSharp.dll (managed .NET assembly which contains the core CefSharp functionality)
• CefSharp.WinForms.dll or CefSharp.WPF.dll (depending on your project type)

See CefSharp - Frequently asked questions.

I have just had problems with this as well and I did the following:

• check that all files are in the apps root directory (https://github.com/cefsharp/CefSharp/wiki/Output-files-description-table-%28Redistribution%29 and https://bitbucket.org/chromiumembedded/cef/src/aefb5ccce879f308f0bcc3ac719c86defe2f9715/tools/distrib/win/README.redistrib.txt?at=master&fileviewer=file-view-default)
• made sure the C++ Redist was installed (in fact I have 2010, 2013, 2015 all x86 and x64 installed)

• added the following code during startup to ensure all dependencies are there

      string dir = AppDomain.CurrentDomain.BaseDirectory;
      var missingDeps = CefSharp.DependencyChecker.CheckDependencies(true, false, dir, string.Empty,
          Path.Combine(dir, "CefSharp.BrowserSubprocess.exe"));
      if (missingDeps?.Count > 0)
          throw new InvalidOperationException("Missing components:\r\n  " + string.Join("\r\n  ", missingDeps));
      // ReSharper disable once UnusedVariable
      var browser = new CefSharp.Wpf.ChromiumWebBrowser(); //test, if browser can be instantiated
  

CefSharp.DependencyChecker did not report anything missing but as soon as I called new CefSharp.Wpf.ChromiumWebBrowser() the exception occured.

I checked all ms.net CEF dlls using ILSpy and found that some of these DLLs were also located in the GAC. As soon as I removed them from GAC all worked ok!

This is a common problem and is therefore mentioned in the FAQ, question number 3.

@AcccessDenied is right. The files need to be present in your output folder (bin\Debug or bin\Release). One way to make this is by using a Post-Build action, which can set under the project settings in Visual Studio.

You can also set up the post-build in the .csproj file, somewhat like this:

<Target Name="AfterBuild">
  <ItemGroup>
    <CefBinaries Include="$(SolutionDir)CEF\$(UnmanagedPlatform)\*.*" />
    <LocaleFiles Include="$(SolutionDir)CEF\locales\*.*" />
    <SubProcessFiles Include="$(SolutionDir)$(UnmanagedPlatform)\$(Configuration)\CefSharp.BrowserSubprocess.exe" />
  </ItemGroup>
  <Copy SourceFiles="@(CefBinaries)" DestinationFolder="$(TargetDir)" />
  <Copy SourceFiles="@(LocaleFiles)" DestinationFolder="$(TargetDir)locales" />
  <Copy SourceFiles="@(SubProcessFiles)" DestinationFolder="$(TargetDir)" />
</Target>

(This example is taken from the CefSharp.Wpf.Example project in the CefSharp source code, CefSharp3 branch. The exact file locations may vary in your case, especially if using CefSharp1, so adapt it as needed to ensure the files get copied correctly.)

I don't recommend putting stuff in bin\Debug or bin\Release and adding it to the solution using Copy Always. It feels like a kludge to me.

I had offline CEF working perfectly, then it suddenly stopped working after upgrading solution to core 3.1. Still not sure why, but copying in resources, VC++ runtimes, etc. and other usual solutions didn't work. I added the following code for diagnostic purposes in my startup code and suddenly, CEF works again. Assemblies were in same path, but it seems loading them clued in the assembly binder. If anyone is similarly frustrated, might try similar approach with whatever variant of CEF assemblies you are working with. Maybe some .net gurus can explain exactly why this helps.

  try
  {
    Assembly asm;
    string path;

    path = Path.Combine(
      Directory.GetCurrentDirectory(),
      "CefSharp.Core.dll");
    asm = Assembly.LoadFrom(path);
    path = Path.Combine(
      Directory.GetCurrentDirectory(),
      "CefSharp.OffScreen.dll");
    asm = Assembly.LoadFrom(path);
  }
  catch (Exception exception)
  {
    System.Diagnostics.Trace.WriteLine(exception.Message + " @ " + exception.StackTrace);
  }

*** Updates below after @amaitland offered the pertinent information, thanks! As per https://github.com/cefsharp/CefSharp.MinimalExample#net-core-support I updated my project to include:

<ItemGroup>
  <Reference Update="CefSharp">
    <Private>true</Private>
  </Reference>
  <Reference Update="CefSharp.Core">
    <Private>true</Private>
  </Reference>
  <Reference Update="CefSharp.OffScreen">
    <Private>true</Private>
  </Reference>
</ItemGroup>

and it no longer needs the previous code block to work out of the box. If anyone runs into confusion like I did, adding privateassets all to the PACKAGE reference is not the same thing. Rather than typing in those lines, you can also expand 'Assemblies' in the solution explorer for your project, and right click on the CefSharp assemblies there and change CopyLocal to Yes. Thanks again, @amaitland

You have to set the 'copy to output' properties of the files to 'copy always' or 'copy if newer'. This copies all the files to the output directory, as stated by Coder.

In my case, I was following the steps outlined in CefSharp - Our Code World.

Instead of following step A and adding CefSharpAnyCpuSupport in csproj and probing in App.config, simply setting the Platform Target to x86 in step B did the trick.

The recommended way seems to be to use the NuGet package. Even then you need to make some non-intuitive changes but they are documented. When installing the package freshly a readme.txt file opens with most common issues.

In my case I was missing (x64 also available)

<probing privatePath="x86" />

My App.config looks like this (with CommonServiceLocator in it, ignore that part if you don't have it)

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.2" />
    </startup>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <probing privatePath="x86" />

      <dependentAssembly>
        <assemblyIdentity name="CommonServiceLocator" publicKeyToken="489b6accfaf20ef0" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-2.0.3.0" newVersion="2.0.3.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

The error occurs because there is really no Cefsharp DLL in the bin folder when you set the project to AnyCPU. But in the x86 and x64 folder bellow where you are probing when adding this line the DLL exists. A temporary fix would be to copy the contents from /bin/x86 to /bin.

If AnyCpu is desired CefSharpAnyCpuSupport needs to be added to csproj file. The project Flag for Prefer 32bit needs to be set.

1. Make sure all dependent libraries are copied to debug/release folder
2. If you build CEFSharp libs by your own, make sure the build configuration matches. That is, if you build your application in Release mode , x86 then you must build CEFSharp libs also in Release, x86. Other wise it will throw dll not found error

I found that one of the project platform is mentioned as x64. I changed it to "Any CPU" it works fine.