NuGet: package with source code that can be referenced as library

Is there any possibility to create a NuGet package containing the source code that can be referenced as library? When I use the .nuspec for packing the created .nupkg contains the source code but cannot be referenced. I have already tried out to add a library node within the .nuspec as some suggested on SO but the resulting .nuspec does not match the standard and thus cannot be created. When using .csproj for packing the .nupkg does only contain the .dll. It can be referenced but cannot be debugged because it does not contain any source code. How could I achieve both? A referanceable library that contains source code. In advance thank you for your time.

Solution

Here's a .nuspec file I use to package sources from multiple directories that get used as a library in other projects:

<?xml version="1.0"?>
<package >
  <metadata>
    <id>Your.Package</id>
    <version>1.0.14</version>
    <authors>me</authors>
    <owners>me</owners>
    <requireLicenseAcceptance>false</requireLicenseAcceptance>
    <description>Class library.</description>
    <releaseNotes>Initial release.</releaseNotes>
    <copyright>Copyright 2017</copyright>
    <tags>some tags</tags>
  </metadata>
  <files>
    <file src="*.cs" target="content/App_Packages/<YourPackage>.Sources" />
    <file src="Configuration/*.cs" target="content/App_Packages/<YourPackage>.Sources" />
  </files>
</package>

Just change the "file" tags to reference the files you're trying to include.

When you're ready to create the .nupkg file, cd to the directory containing your .nuspec file and run: nuget pack .nuspec