Error when accessing a file from a NuGet Package

I am creating a nuget package with custom controls, when I referenced the project directly everything was fine, but when I generate the nuget package and install it in the target project I get an error saying that the specified file cannot be found.For a class library it was enough to add the prefix "ms-appx:///[project-name]" but for a nuget package this doesn't seem to work, is there any prefix to access a file from a package?

string pathBase = "ms-appx:///Msb.UI.for.UWP/Assets/ControlsVersions/";private void UpdateSource(){    var path = pathBase + ControlsVersion.ToString() +".xaml";    this.Source = new Uri(path, UriKind.RelativeOrAbsolute);}