Multiple C# projects in the same root directory?

[geekox86]

I have a root directory with multiple C# projects (*.csproj).
I need MSBuild to filter the C# source files by root namespace for each project, since they share the same root directory.
Otherwise, I will get error CS0017: Program has more than one entry point defined when I try to run a project using dotnet run --project Project1.csproj.
My project folder structure is organized based on features, and I want all source files related to a feature from all projects (e.g. server, client, test) to be inside the feature specific sub-folder.

Sample solution structure:

|_ Project1.csproj
|_ Project2.csproj
|_ Program1.cs (this contains main for Project1 under root namespace P1)
|_ Program2.cs (this contains main for Project2 under root namespace P2)
|_ Feature1 (this feature belongs to Project1 under root namespace P1)
|  |_ SomeClass1.cs
|  |_ SomeClass1.test.cs
|_ Feature2 (this feature belongs to Project2 under root namespace P2)
   |_ SomeClass2.cs
   |_ SomeClass2.test.cs

Now, how can I run/build Project1.csproj such that MSBuild will only include Program1.cs and SomeClass1.cs. Similar thing with Project2.csproj with Program2.cs and SomeClass2.cs. Can I ask MSBuild to include only files/types based on their root namespace?

Any idea how to go about this?

[drewnoakes]

To fix the multiple entry point issue, in Project1.csproj you could add:

<ItemGroup>
    <Compile Remove="Program*.cs" />
    <Compile Include="Program1.cs" />
</ItemGroup>

It does seem like this would be easier to achieve with multiple projects though.

[KalleOlaviNiemitalo]

The Exclude attribute only prevents items from being added by an Include attribute in the same element:

msbuild/src/Build/Evaluation/ProjectParser.cs

Lines 292 to 293 in 39993bd

	// Exclude must be missing, unless Include exists
	ProjectXmlUtilities.VerifyThrowProjectInvalidAttribute(exclude.Length == 0 || include.Length > 0, (XmlAttributeWithLocation)element.Attributes[XMakeAttributes.exclude]);

You might instead need the Remove attribute, or properties listed in Default item inclusion properties.

In addition, you should set the BaseIntermediateOutputPath property so that the files generated from these projects or added by NuGet do not conflict.

[drewnoakes]

I see I also used Exclude instead of Include. I've updated the snippet.

[Nirmal4G]

If you're using .NET SDK then set EnableDefaultItems property to false and manually include them by a pattern from which you can isolate them in the includes.

Example:

<PropertyGroup>
    <EnableDefaultItems>False</EnableDefaultItems>
</PropertyGroup>

<!-- Project 1 -->
<ItemGroup>
    <Compile Include="*/**/*_P1.cs" Exclude="$(DefaultExcludesInProjectFolder);$(DefaultItemExcludes)" />
</ItemGroup>

<!-- Project 2 -->
<ItemGroup>
    <Compile Include="*/**/*_P2.cs" Exclude="$(DefaultExcludesInProjectFolder);$(DefaultItemExcludes)" />
</ItemGroup>

For more info, see default item inclusions in Microsoft.NET.Sdk.