Hello :)

For example.

Startup project: I configure and create Owin App.

Core project: This project is core. In this project, all the magic happens.

But! I want to configure DB connection for Core project in Startup project and have these settings in classes of a Core project project.

I believe that it should be done like this:

class Strartup
{
    public void Configuration(IAppBuilder app)
    {
        app.Properties.Add("ConnectionString", "SomeString");
    }
}

class SomeClass
{
    // And getting this string in the other classes
    public void SomeMethod()
    {
        string connectionString = SomeObject.GetContext().Properties.Get("ConnectionString");
    }
}