Using Chilkat Mono in a Visual Studio C# Project

The Chilkat Mono assembly can be used in a Visual Studio project (any version of Visual Studio).

(From a programming perspective, using the Chilkat Mono classes is the same as using the Chilkat .NET classes. The Chilkat .NET assemblies (available from Chilkat .NET Downloads are mixed-mode assemblies. The outer-layer is fully managed, and the inner core contains the native C++ implementation. The Chilkat Mono solution is different: The .NET/Mono assembly is 100% managed, and there is a 2nd DLL that contains the native C++ implementation. The 100% managed assembly (internally) calls into the native DLL using P/Invoke.)

Actually.. you don’t even need to build the 100% managed assembly.  You can instead just add the Chilkat *.cs source files to your project directly.  (If you open one of the .cs source files, you’ll see how P/Invoke is used.)

  1. Created a Visual Studio project in C:\MyProject
  2. Downloaded the Chilkat Mono .zip from  and unzipped in C:\MyProject
  3. You now have a directory c:\MyProject\chilkatMono-9.5.0.    Within that directory, I have a chilkatCs directory, and a nativeDll directory.
  4. Add all of the .cs source files from chilkatCs to your Visual Studio C# project.  (Note: If you find an “Accounts.cs” source file, delete it and do not add it.)
  5. You don’t necessarily need to add all of the .cs sources, but you must add whatever is necessary to resolve all references.  For example, if you add MailMan.cs, you’ll certainly need to add Email.cs, and that in turn will require Cert.cs, etc.  A good strategy is to add everything, then delete various things that are likely unreferenced by other things.  For example, you can safely get rid of Csr.cs if not using CSR’s.
  6. Add code to your app.  For example:

    Chilkat.Zip zip = new Chilkat.Zip();

  7. You can try building and running, but it’ll fail because the native DLL won’t be found..
  8. Copy the desired 32-bit or 64-bit native DLL into the same directory where your .exe is created.  For example, copy c:\MyProject\chilkatMono-9.5.0\nativeDll\windows\x64\chilkatMono-9_5_0.dll to c:\MyProject\bin\Debug
  9. Assuming your Visual Studio project is “Any CPU”, and you don’t have a “Prefer 32-bit” checkbox checked (in Project Settings), and that you’re running on a 64-bit system, then the .NET runtime should locate and load the 64-bit chilkatMono-9_5_0.dll, and your program runs fine.

Chilkat .NET Assemblies – Matching Visual Studio versions to .NET Framework Versions to VC++ Runtime Versions.


The .NET Framework version that corresponds to each Visual Studio release is as follows:

VS2017 — .NET 4.6, .NET 4.7
VS2015 — .NET 4.6
VS2013 — .NET 4.5 (actually 4.5.1, but we only care about major/minor numbers)
VS2012 — .NET 4.5
VS2010 — .NET 4.0
VS2008 — .NET 3.5
VS2005 — .NET 2.0

When using Chilkat .NET for a particular .NET Framework version, the corresponding VC++ Runtime redist (from Microsoft) needs to be installed on the system. The VC++ redist that is needed, and the download links, are shown below:

VS2017 .NET 4.6/4.7 Chilkat .NET for 4.6/4.7 needs VC++ 2017 runtime  
VS2015 .NET 4.6 Chilkat .NET for 4.6 needs VC++ 2015 runtime (also known as VC++ 14)
VS2013 .NET 4.5 Chilkat .NET for 4.5 (built with VS2013) needs VC++ 2013 runtime (also known as VC++ 12)
VS2012 .NET 4.5 Chilkat .NET for 4.5 (built with VS2012) needs VC++ 2012 runtime (also known as VC++ 11)
VS2010 .NET 4.0 Chilkat .NET for 4.0 needs VC++ 2010 runtime (x86)(x64) (also known as VC++ 10)
VS2005/2008 .NET 2.0/3.5 Chilkat .NET for 2.0/3.5 needs VC++ 2005 runtime (x86)(x64) (also known as VC++ 8)

Dynamically Loading a 32-bit or 64-bit .NET Assembly at Runtime

The Chilkat .NET assembly is a mixed-mode assembly, meaning that it exposes a managed API, but the inner core is native. Therefore, as for any DLL, a 32-bit process must load a 32-bit DLL, and a 64-bit process must load a 64-bit DLL.

On a 32-bit system, there is never any choice and therefore this whole subject is moot.

On a 64-bit system, a 100% managed .NET app can run as either a 64-bit process or as a 32-bit process. Visual Studio projects have a setting named “Prefer 32-bit”, which is by-default ON, which means the app will always run as a 32-bit process. In that case, it is the 32-bit DLL that must be loaded (always), and again this subject is moot.

I recommend this: If your app does not use more than 4GB of memory, then simply choose to run 32-bit everywhere. You have better things to do with your time. Performance is usually just as good (if not better) running 32-bit.

I also recommend this: As time goes on, it gets more and more difficult to find yourself actually running on a 32-bit system. I’m sure it’s been many years since it’s been possible to buy a new computer running 32-bit Windows, and Microsoft is ending support for the OS’s what can run 32-bit Windows. So.. if your app will NEVER encounter a 32-bit system, and it needs more than 4GB of memory, then uncheck the “Prefer 32-bit” setting in your Visual Studio app, and ALWAYS run 64-bit. Again, you have better things to do with your time than monkeying around with additional unnecessary complexity.

If you’re in the situation where you desire either 32-bit or 64-bit, then there are two solutions:

  1. Make sure the 32-bit Chilkat DLL is distributed with your app to systems where it will run 32-bit, and the 64-bit Chilkat DLL is distributed with your app to systems where it will run 64-bit. Or…
  2. Dynamically load either the 32-bit or 64-bit DLL at runtime. Here are links to two possible solutions for doing so.

Dynamically Loading .NET Assembly (32-bit or 64-bit)

Found a nice technique for dynamically loading a native .NET assembly and automatically choosing the appropriate one to match the loading process’s address space (32-bit or 64-bit). The source is located here: and reproduced here:

I prefer another solution to this problem. It allows you to have a mix of 32 and 64 bit apps in the same directory.

I install both 32 and 64 bit assemblies into the same directory by renaming them.


In the project references you just refer to the one you want for that particular project.

Then I get them to load using the AssemblyResolve event which fires when a dll can’t be found.

In Program.Main() add this

	AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;

Then add this code somewhere

	private const string ChilkatRootFileName = "ChilkatDotNet4";

	static Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
		if (args.Name.StartsWith(ChilkatRootFileName, StringComparison.InvariantCultureIgnoreCase))
			string path = string.Empty;
			string current_folder = string.Empty;
				current_folder = Path.GetDirectoryName(new Uri(
				path = Path.Combine(current_folder, ChilkatRootFileName + 
					string.Format("-{0}.dll", IntPtr.Size == 4 ? "32" : "64"));
				Assembly assembly = Assembly.LoadFrom(path);
				return assembly;
			catch (Exception ex)
		return null;