What's a csproj.in file?

[CeaseHarping]

Forgive me if it's a dumb question, but what process do I follow/is required to be executed to turn the csproj.in files into csproj files so I can open the solution? It seems like they have variable placeholders inside but I've never looked so deeply at what a csproj is supposed to look like..

[Mizux]

When using Make of CMake based build we will generate the .Net Foo.csproj project file from a template call Sample.csproj.in (note: this is a CMake convention to add .in for "template" files).

You can find them here:
src: https://github.com/google/or-tools/tree/master/ortools/dotnet

CMake

For variables i.e. @FOO@ you can take a look at

or-tools/CMakeLists.txt

Lines 10 to 13 in 2cb85b4

	message(STATUS "${PROJECT_NAME} version: ${PROJECT_VERSION}")
	#message(STATUS "major: ${PROJECT_VERSION_MAJOR}")
	#message(STATUS "minor: ${PROJECT_VERSION_MINOR}")
	#message(STATUS "patch: ${PROJECT_VERSION_PATCH}")

or-tools/cmake/dotnet.cmake

Lines 30 to 50 in 2cb85b4

	# Needed by dotnet/CMakeLists.txt
	set(DOTNET_PACKAGE Google.OrTools)
	set(DOTNET_PACKAGES_DIR "${PROJECT_BINARY_DIR}/dotnet/packages")
	if(APPLE)
	set(RUNTIME_IDENTIFIER osx-x64)
	elseif(UNIX)
	set(RUNTIME_IDENTIFIER linux-x64)
	elseif(WIN32)
	set(RUNTIME_IDENTIFIER win-x64)
	else()
	message(FATAL_ERROR "Unsupported system !")
	endif()
	set(DOTNET_NATIVE_PROJECT ${DOTNET_PACKAGE}.runtime.${RUNTIME_IDENTIFIER})
	message(STATUS ".Net runtime project: ${DOTNET_NATIVE_PROJECT}")
	set(DOTNET_NATIVE_PROJECT_DIR ${PROJECT_BINARY_DIR}/dotnet/${DOTNET_NATIVE_PROJECT})
	message(STATUS ".Net runtime project build path: ${DOTNET_NATIVE_PROJECT_DIR}")
	set(DOTNET_PROJECT ${DOTNET_PACKAGE})
	message(STATUS ".Net project: ${DOTNET_PROJECT}")
	set(DOTNET_PROJECT_DIR ${PROJECT_BINARY_DIR}/dotnet/${DOTNET_PROJECT})
	message(STATUS ".Net project build path: ${DOTNET_PROJECT_DIR}")

and we have a CMake function to generate it
add_dotnet_example(File.cs)
https://github.com/google/or-tools/blob/master/cmake/dotnet.cmake#L361-L422

  configure_file(
    ${PROJECT_SOURCE_DIR}/ortools/dotnet/Sample.csproj.in
    ${DOTNET_EXAMPLE_DIR}/${EXAMPLE_NAME}.csproj
    @ONLY)

Makefile

Same story but using $(SED) program:
variables:

or-tools/makefiles/Makefile.dotnet.mk

Lines 67 to 74 in 2cb85b4

	DOTNET_ORTOOLS_ASSEMBLY_NAME := Google.OrTools
	DOTNET_ORTOOLS_RUNTIME_ASSEMBLY_NAME := $(DOTNET_ORTOOLS_ASSEMBLY_NAME).runtime.$(DOTNET_RUNTIME_IDENTIFIER)
	DOTNET_ORTOOLS_NATIVE := google-ortools-native
	DOTNET_ORTOOLS_NUPKG := $(DOTNET_PACKAGE_DIR)/$(DOTNET_ORTOOLS_ASSEMBLY_NAME).$(OR_TOOLS_VERSION).nupkg
	DOTNET_ORTOOLS_RUNTIME_NUPKG := $(DOTNET_PACKAGE_DIR)/$(DOTNET_ORTOOLS_RUNTIME_ASSEMBLY_NAME).$(OR_TOOLS_VERSION).nupkg
	FSHARP_ORTOOLS_ASSEMBLY_NAME := $(DOTNET_ORTOOLS_ASSEMBLY_NAME).FSharp
	FSHARP_ORTOOLS_TESTS_ASSEMBLY_NAME := $(DOTNET_ORTOOLS_ASSEMBLY_NAME).FSharp.Tests
	FSHARP_ORTOOLS_NUPKG := $(DOTNET_PACKAGE_DIR)/$(FSHARP_ORTOOLS_ASSEMBLY_NAME).$(OR_TOOLS_VERSION).nupkg

and recipe .csproj.in to .csproj

or-tools/makefiles/Makefile.dotnet.mk

Lines 566 to 585 in 2cb85b4

	$$(TEMP_DOTNET_DIR)/$1/%/%.csproj: \
	$${SRC_DIR}/ortools/dotnet/Sample.csproj.in \
	| $$(TEMP_DOTNET_DIR)/$1/%
	$$(SED) -e "s/@DOTNET_PACKAGES_DIR@/..\/..\/packages/" \
	ortools$$Sdotnet$$SSample.csproj.in \
	> $$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
	$$(SED) -i -e 's/@DOTNET_PROJECT@/$$(DOTNET_ORTOOLS_ASSEMBLY_NAME)/' \
	$$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
	$$(SED) -i -e 's/@SAMPLE_NAME@/$$*/' \
	$$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
	$$(SED) -i -e 's/@PROJECT_VERSION@/$$(OR_TOOLS_VERSION)/' \
	$$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
	$$(SED) -i -e 's/@PROJECT_VERSION_MAJOR@/$$(OR_TOOLS_MAJOR)/' \
	$$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
	$$(SED) -i -e 's/@PROJECT_VERSION_MINOR@/$$(OR_TOOLS_MINOR)/' \
	$$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
	$$(SED) -i -e 's/@PROJECT_VERSION_PATCH@/$$(GIT_REVISION)/' \
	$$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj
	$$(SED) -i -e 's/@FILE_NAME@/$$*.cs/' \
	$$(TEMP_DOTNET_DIR)$$S$1$$S$$*$$S$$*.csproj

BTW you should not write a csproj.in by hand and for .csproj you can copy paste one of the example archive.
todo(mizux): Document how to create a exampel project from scratch using VisualStudio "new cs project" or dotnet cli dotnet new console...