diff --git a/README.md b/README.md
index 12a376d..e04b4d5 100644
--- a/README.md
+++ b/README.md
@@ -2,4 +2,14 @@ Parts of this project based on code by Illumina.
 
 For more info:
 
-https://github.com/Illumina/interop
\ No newline at end of file
+https://github.com/Illumina/interop
+
+## `.csproj` support
+It is possible to include eg. a C# project `.csproj` file with the `add_dotnet_project` function.
+This `.csproj` file must include a line
+
+```xml
+<Import Project="obj/CMake.g.props"/>
+```
+
+as this is where CMake generates references to other ROS 2 packages in, as well as the output path and the assembly name.
diff --git a/cmake/Modules/FindDotNETExtra.cmake b/cmake/Modules/FindDotNETExtra.cmake
index 81c214c..a3085b7 100644
--- a/cmake/Modules/FindDotNETExtra.cmake
+++ b/cmake/Modules/FindDotNETExtra.cmake
@@ -107,6 +107,79 @@ function(add_dotnet_test _TARGET_NAME)
 
 endfunction()
 
+function(add_dotnet_library_project _TARGET_NAME)
+  cmake_parse_arguments(_add_dotnet_library_project
+    ""
+    ""
+    "PROJ;INCLUDE_DLLS"
+    ${ARGN}
+  )
+
+  csharp_add_existing_project(${_TARGET_NAME}
+    PROJ
+    ${_add_dotnet_library_project_PROJ}
+    ${_add_dotnet_library_project_UNPARSED_ARGUMENTS}
+    INCLUDE_DLLS
+    ${_add_dotnet_library_project_INCLUDE_DLLS}
+  )
+endfunction()
+
+function(add_dotnet_executable_project _TARGET_NAME)
+  cmake_parse_arguments(_add_dotnet_executable_project
+    ""
+    ""
+    "PROJ;INCLUDE_DLLS"
+    ${ARGN}
+  )
+
+  csharp_add_existing_project(${_TARGET_NAME}
+    EXECUTABLE
+    PROJ
+    ${_add_dotnet_executable_project_PROJ}
+    ${_add_dotnet_executable_project_UNPARSED_ARGUMENTS}
+    INCLUDE_DLLS
+    ${_add_dotnet_executable_project_INCLUDE_DLLS}
+  )
+endfunction()
+
+function(add_dotnet_test_project _TARGET_NAME)
+  # TODO: (sh) It seems the test project gets build twice with different output directories
+  # e.g.: the same output files are contained in "build/<package>/<target>/net6.0/" and "build/<package>/<target>/net6.0/linux-x64"
+  # But this seems to be the case with other projects as well (package rcldotnet and targets rcldotnet_assemblies and test_messages).
+  # So maybe this is how it should be, but why?
+
+  cmake_parse_arguments(_add_dotnet_test_project
+    ""
+    ""
+    "PROJ;INCLUDE_DLLS"
+    ${ARGN}
+  )
+
+  csharp_add_existing_project(${_TARGET_NAME}
+    EXECUTABLE
+    PROJ
+    ${_add_dotnet_test_project_PROJ}
+    ${_add_dotnet_test_project_UNPARSED_ARGUMENTS}
+    INCLUDE_DLLS
+    ${_add_dotnet_test_project_INCLUDE_DLLS}
+  )
+
+  if(CSBUILD_PROJECT_DIR)
+    set(CURRENT_TARGET_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/${CSBUILD_PROJECT_DIR}")
+  else()
+    set(CURRENT_TARGET_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
+  endif()
+
+  get_filename_component(_add_dotnet_test_project_PROJ_ABSOLUTE ${_add_dotnet_test_project_PROJ} ABSOLUTE)
+
+  ament_add_test(
+    ${_TARGET_NAME}
+    GENERATE_RESULT_FOR_RETURN_CODE_ZERO
+    WORKING_DIRECTORY ${CURRENT_TARGET_BINARY_DIR}/${_TARGET_NAME}
+    COMMAND dotnet test ${_add_dotnet_test_project_PROJ_ABSOLUTE}
+  )
+endfunction()
+
 function(install_dotnet _TARGET_NAME)
     get_target_property(_target_executable ${_TARGET_NAME} EXECUTABLE)
     get_target_property(_target_path ${_TARGET_NAME} OUTPUT_PATH)
diff --git a/cmake/Modules/dotnet/CMake.g.props.in b/cmake/Modules/dotnet/CMake.g.props.in
new file mode 100644
index 0000000..64491ef
--- /dev/null
+++ b/cmake/Modules/dotnet/CMake.g.props.in
@@ -0,0 +1,8 @@
+<Project>
+  <ItemGroup>
+@CSHARP_BUILDER_INCLUDE_DLLS_STR@  </ItemGroup>
+  <PropertyGroup>
+    <OutputPath>@CSHARP_BUILDER_OUTPUT_PATH_NATIVE@</OutputPath>
+    <AssemblyName>@_TARGET_NAME@</AssemblyName>
+  </PropertyGroup>
+</Project>
diff --git a/cmake/Modules/dotnet/UseCSharpProjectBuilder.cmake b/cmake/Modules/dotnet/UseCSharpProjectBuilder.cmake
index 523c0a7..c51ca03 100644
--- a/cmake/Modules/dotnet/UseCSharpProjectBuilder.cmake
+++ b/cmake/Modules/dotnet/UseCSharpProjectBuilder.cmake
@@ -192,3 +192,82 @@ function(csharp_add_project name)
         ${DOTNET_CORE_FOUND}
     )
 endfunction()
+
+function(csharp_add_existing_project name)
+    if(CSBUILD_PROJECT_DIR)
+        set(CURRENT_TARGET_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/${CSBUILD_PROJECT_DIR}")
+    else()
+        set(CURRENT_TARGET_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
+    endif()
+    set(CSBUILD_PROJECT_DIR "")
+    file(MAKE_DIRECTORY ${CURRENT_TARGET_BINARY_DIR}/${name})
+    cmake_parse_arguments(_csharp_add_existing_project
+        "EXECUTABLE"
+        ""
+        "PROJ;INCLUDE_DLLS"
+        ${ARGN}
+    )
+
+    foreach(it ${_csharp_add_existing_project_INCLUDE_DLLS})
+        file(TO_NATIVE_PATH ${it} nit)
+        list(APPEND refs "    <Reference Include=\"${nit}\"/>\n")
+    endforeach()
+
+    list(LENGTH refs REFERENCE_COUNT)
+
+    if(REFERENCE_COUNT GREATER 0)
+        set(refs_concat "${refs}")
+    else()
+        set(refs_concat "")
+    endif()
+
+    get_filename_component(_csharp_add_existing_project_PROJ_PATH ${_csharp_add_existing_project_PROJ} DIRECTORY)
+    get_filename_component(_csharp_add_existing_project_PROJ_PATH_ABSOLUTE ${_csharp_add_existing_project_PROJ_PATH} ABSOLUTE)
+
+    get_filename_component(_csharp_add_existing_project_PROJ_ABSOLUTE ${_csharp_add_existing_project_PROJ} ABSOLUTE)
+
+    set(_csharp_add_existing_project_PROPS_PATH ${_csharp_add_existing_project_PROJ_PATH_ABSOLUTE}/obj/CMake.g.props)
+
+    set(CSHARP_BUILDER_OUTPUT_PATH ${CMAKE_CURRENT_BINARY_DIR}/${name}/${CMAKE_BUILD_TYPE})
+    file(TO_NATIVE_PATH ${CSHARP_BUILDER_OUTPUT_PATH} CSHARP_BUILDER_OUTPUT_PATH_NATIVE)
+
+    # TODO: add to add_custom_target to avoid writing every time
+    string (REPLACE ";" "" CSHARP_BUILDER_INCLUDE_DLLS_STR "${refs_concat}")
+    set(CSHARP_BUILDER_INCLUDE_DLLS ${refs_concat})
+    configure_file(${dotnet_cmake_module_DIR}/Modules/dotnet/CMake.g.props.in ${_csharp_add_existing_project_PROPS_PATH} @ONLY)
+
+    if(${_csharp_add_existing_project_EXECUTABLE} AND NOT DOTNET_CORE_FOUND)
+        set(ext "exe")
+    else()
+        set(ext "dll")
+    endif()
+
+    add_custom_target(
+        ${name} ALL
+
+        COMMAND ${RESTORE_CMD}
+
+        COMMAND ${CSBUILD_EXECUTABLE} ${CSBUILD_RESTORE_FLAGS} ${_csharp_add_existing_project_PROJ_ABSOLUTE}
+        COMMAND ${CSBUILD_EXECUTABLE} ${CSBUILD_BUILD_FLAGS} ${_csharp_add_existing_project_PROJ_ABSOLUTE}
+        WORKING_DIRECTORY ${CURRENT_TARGET_BINARY_DIR}/${name}
+        COMMENT "${RESTORE_CMD};${CSBUILD_EXECUTABLE} ${CSBUILD_RESTORE_FLAGS} ${_csharp_add_existing_project_PROJ_ABSOLUTE}; ${CSBUILD_EXECUTABLE} ${CSBUILD_BUILD_FLAGS} ${_csharp_add_existing_project_PROJ_ABSOLUTE} -> ${CURRENT_TARGET_BINARY_DIR}/${name}"
+
+        # TODO: How to deal with changes to *.cs files (Implicit include in *.csproj)
+        # DEPENDS ${sources_dep}
+        DEPENDS ${_csharp_add_existing_project_PROJ_ABSOLUTE}
+    )
+
+    set(DOTNET_OUTPUT_PATH ${CSHARP_BUILDER_OUTPUT_PATH}/${CSHARP_TARGET_FRAMEWORK}/${DOTNET_CORE_RUNTIME}/publish/)
+
+    set_target_properties(${name}
+        PROPERTIES
+        EXECUTABLE
+        ${_csharp_add_existing_project_EXECUTABLE}
+        OUTPUT_PATH
+        ${DOTNET_OUTPUT_PATH}
+        OUTPUT_NAME
+        ${name}${CSBUILD_OUTPUT_SUFFIX}.${ext}
+        DOTNET_CORE
+        ${DOTNET_CORE_FOUND}
+    )
+endfunction()