C#/Win32 P/Invoke Source Generator
A source generator to add a user-defined set of Win32 P/Invoke methods and supporting types to a C# project.
Features
- Rapidly add P/Invoke methods and supporting types to your C# project.
- No bulky assemblies to ship alongside your application.
SafeHandle
-types automatically generated.- Generates xml documentation based on and links back to docs.microsoft.com
Prerequisites
The .NET 5 SDK or Visual Studio 2019 Update 8 (16.8) for the C# compiler that added support for Source Generators. The experience with source generators in Visual Studio is still improving, and is noticeably better in VS 16.9. WPF projects have additional requirements.
In addition, some generated code may require use of the C# 9 language version (<LangVersion>9</LangVersion>
) in your project file. See issue #4 for more on this.
See dotnet/pinvoke for precompiled NuGet packages with Win32 P/Invokes.
Usage
Install the Microsoft.Windows.CsWin32
package:
dotnet add package Microsoft.Windows.CsWin32 --prerelease
Your project must allow unsafe code to support the generated code that will likely use pointers.
This does not automatically make all your code unsafe.
Use of the unsafe
keyword is required anywhere you use pointers.
The source generator NuGet package sets the default value of the AllowUnsafeBlocks
property for your project to true
,
but if you explicitly set it to false
in your project file, generated code may produce compiler errors.
Create a NativeMethods.txt
file in your project directory that lists the APIs to generate code for.
Each line may consist of one of the following:
- Exported method name (e.g.
CreateFile
). This may include theA
orW
suffix, where applicable. This may be qualified with a namespace but is only recommended in cases of ambiguity, which CsWin32 will prompt where appropriate. - A namespace to generate all APIs from (e.g.
Windows.Win32.Storage.FileSystem
would search the metadata for all APIs within that namespace and generate them). - Module name followed by
.*
to generate all methods exported from that module (e.g.Kernel32.*
). - The name of a struct, enum, constant or interface to generate. This may be qualified with a namespace but is only recommended in cases of ambiguity, which CsWin32 will prompt where appropriate.
- A comment (i.e. any line starting with
//
) or white space line, which will be ignored.
When generating any type or member, all supporting types will also be generated.
Generated code is added directly in the compiler. An IDE may make this generated code available to view through code navigation commands (e.g. Go to Definition) or a tree view of source files that include generated source files.
Assuming default settings and a NativeMethods.txt
file with content that includes CreateFile
, the P/Invoke methods can be found on the Windows.Win32.PInvoke
class, like this:
using Windows.Win32;
PInvoke.CreateFile(/*args*/);
Constants are defined on the Windows.Win32.Constants
class.
Other supporting types are defined within or under the Windows.Win32
namespace.
Discovery of the namespace for a given type can be done with the Go To All feature (Ctrl+T) in Visual Studio with the type name as the search query.
Customizing generated code
Several aspects of the generated code can be customized, including:
- The name of the class(es) that declare p/invoke methods
- The namespace that declares all interop types
- Whether to emit interop types as
public
orinternal
- Whether to emit ANSI functions as well where Wide character functions also exist
- Set
PreserveSig
for COM interfaces or individual members - Force generation of blittable structs, COM structs instead of interfaces (for super high performance with 0 GC pressure), etc.
To configure these settings, create a NativeMethods.json
file in your project directory.
Specifying the $schema
property adds completions, descriptions and validation in many JSON editors.
{
"$schema": "https://aka.ms/CsWin32.schema.json",
"emitSingleFile": false
}
Most generated types include the partial
modifier so you can add your own members to that type within your code.
When you need to replace a generated type, simply copy and paste it from generated code into your own source files
and remove the partial
modifier.
Be sure to keep the name and namespace exactly the same.
CsWin32 will notice that your project already declares the type and skip generating it, but generate everything else.
Note that if that type is the only thing that references some other generated type, CsWin32 will stop generating that type too.
To keep CsWin32 generating the referred types you need, add them explicitly to NativeMethods.txt
.
Newer metadata
To update the metadata used as the source for code generation, you may install a newer Microsoft.Windows.SDK.Win32Metadata
package:
dotnet add package Microsoft.Windows.SDK.Win32Metadata -pre
Alternatively, you may set the MicrosoftWindowsSdkWin32MetadataBasePath
property in your project file to the path of the directory containing Windows.Win32.winmd
:
<MicrosoftWindowsSdkWin32MetadataBasePath>c:\path\to\dir</MicrosoftWindowsSdkWin32MetadataBasePath>
Consuming daily builds
Can't wait for the next release to try out a bug fix? Follow these steps to consume directly from our daily build.
Just add this package feed to your nuget.config file:
<add key="winsdk" value="https://pkgs.dev.azure.com/azure-public/winsdk/_packaging/CI/nuget/v3/index.json" />