xmake-csharp

name	xmake-csharp
description	Use when building C# projects with xmake — `.cs` sources with the Mono `mcs` or .NET `dotnet` toolchain, binary / library output, adding references, and mixing with native code via P/Invoke.

Building C# with Xmake

Xmake drives the C# compiler (Mono mcs or modern .NET csc/dotnet) through a target model similar to C++.

1. Minimal project

add_rules("mode.debug", "mode.release")

target("hello")
    set_kind("binary")
    add_files("src/*.cs")

2. Target kinds

target("app")       set_kind("binary")       -- .exe
target("mylib")     set_kind("shared")       -- .dll (class library)

3. Toolchain

xmake f --toolchain=mcs                      -- Mono compiler
xmake f --toolchain=dotnet                   -- .NET SDK (csc)

Pin a specific install with --sdk:

xmake f --toolchain=dotnet --sdk=/usr/share/dotnet/sdk/8.0.100

4. References

target("app")
    add_files("src/*.cs")
    add_csflags("/reference:System.dll", "/reference:System.Core.dll")
    -- Or the modern, portable form:
    add_values("cs.references", "System.dll", "System.Core.dll")

For NuGet / .NET SDK projects, prefer a real .csproj consumed via dotnet build — xmake's direct C# support is best for small / standalone tools.

5. Mixing with native code (P/Invoke)

target("nativelib")
    set_kind("shared")
    add_files("native/*.c")

target("app")
    set_kind("binary")
    add_files("src/*.cs")
    add_deps("nativelib")

In Program.cs:

using System.Runtime.InteropServices;
class Program {
    [DllImport("nativelib")]
    static extern int hello(int x);
}

Xmake places nativelib.dylib/.so/.dll next to the managed binary so the runtime loader finds it.

6. Flags

target("app")
    add_files("src/*.cs")
    add_csflags("-unsafe", "-nowarn:1591")

add_csflags maps to C# compiler flags.

Pitfalls

• xmake is not dotnet build. Complex .csproj projects (NuGet, SDK-style projects, Razor, WPF designers) should go through dotnet build inside a task(...) instead of xmake's native C# support.
• Missing System.dll references. Modern .NET Core doesn't need them (implicit); Mono does. Test with the toolchain you'll ship on.
• Managed DLL + native DLL path mismatch. P/Invoke lookups fail if the native DLL isn't on PATH or next to the .exe. Xmake's default placement handles the common case.

When to branch out

• Native library interop → xmake-targets
• Packaging a C# app → xmake-xpack