initialize DbContext with custom connection string

OurContext.cs

public class OurContext : DbContext
{
	public string ClientKey { get; private set; }

	/// We make use of the DbContext constructor overload that accepts a
	/// connection string to connect to.

	public OurContext(string clientKey)
		: base(GetClientConnectionString(clientKey))
	{
		ClientKey = clientKey;
	}

	/// There's a static method in one of our base assemblies that returns a
	/// client's database connection string based on the client's short name.

	public static string GetClientConnectionString(string clientKey)
	{
		return AClassInOneOfOurBaseAssemblies.GetConnectionString(clientKey);
	}
}