The pack URI in WPF

problem

It's easy to say: First, I built a user-defined control (CustomControl) in a WPF project, and the VS template automatically generated

CustomControl1 and Theme folder (contains a generic.xaml):

Next, I want to move it to a new class library (DLL):

Then I added a reference to the class library in the WPF project, I started trying to use the custom control, and I found that the result was always incorrect, but also

No error. The reason, of course, is that the XAML is not loaded, causing the interface to have no rendering template. Finally, start searching for MSDN and discover outside the WPF application

The PACK://specification is generally used for part-package references.

PACK URI

Table 1: Absolute Pack URIs in tags

File	Absolute Pack URI
Resource file-local assembly	"Pack://application:,,,/resourcefile.xaml"
Resource files in subfolders-Local assemblies	"Pack://application:,,,/subfolder/resourcefile.xaml"
Resource file-referenced assembly	"Pack://application:,,,/referencedassembly;component/resourcefile.xaml"
Resource files in subfolders of referenced assemblies	"Pack://application:,,,/referencedassembly;component/subfolder/resourcefile.xaml"
Resource files in the referenced versioned assembly	"Pack://application:,,,/referencedassembly;v1.0.0.0;component/resourcefile.xaml"
Content Files	"Pack://application:,,,/contentfile.xaml"
Content files in subfolders	"Pack://application:,,,/subfolder/contentfile.xaml"
Source site Files	"Pack://siteoforigin:,,,/soofile.xaml"
Source site files in subfolders	"Pack://siteoforigin:,,,/subfolder/soofile.xaml"

Table 2: Relative Pack URIs in tags

File	Relative Pack URI
Resource files in the local assembly	"/resourcefile.xaml"
Resource files in subfolders of the local assembly	"/subfolder/resourcefile.xaml"
Resource files in the referenced assembly	"/referencedassembly;component/resourcefile.xaml"
Resource files in subfolders of referenced assemblies	"/referencedassembly;component/subfolder/resourcefile.xaml"
Content Files	"/contentfile.xaml"
Content files in subfolders	"/subfolder/contentfile.xaml"

Using the Pack URI in your code

In code, you can specify the pack URI by instantiating the URI class and passing the pack URI as an argument to the constructor. This is illustrated in the following example.

Uri uri = new Uri ("Pack://application:,,,/file.xaml");

By default, the URI class treats the pack URI as an absolute pack URI. Therefore, an exception is thrown when an instance of the URI class is created with a relative pack URI.

Uri uri = new Uri ("/file.xaml");

uri (String, UriKind) overload of the uri class constructor accepts a parameter of type urikind to the Specify whether a pack URI is either absolute or relative." > Fortunately, the,uri  class constructor  uri (String, UriKind)   overloads can accept a type of  urikind The   parameter allows you to specify that the pack URI is absolute

The URI or relative URI.

// Absolute URI (default)
Uri absoluteUri = new Uri("pack://application:,,,/File.xaml", UriKind.Absolute);
// Relative URI
Uri relativeUri = new Uri("/File.xaml", UriKind.Relative);

absolute or relative when You were certain that the provided pack URI was one or the other. " > When you are able to determine whether the provided pack URI is a relative pack URI or an absolute pack URI, you should specify only  Absolute  or  relative.  relativeorabsolute instead." > If you don't know

The type of pack URI used (for example, when the user enters the pack URI at run time), use Relativeorabsolute instead.

// Relative or Absolute URI provided by user via a text box
TextBox userProvidedUriTextBox = new TextBox();
Uri uri = new Uri(userProvidedUriTextBox.Text, UriKind.RelativeOrAbsolute);

So, external resource files, such as videos, images, and so on, the path references need to use the pack URI.
Also, why right-adding new items in the normal class library, no WPF custom control options, can only be built 
manually, or migrated from WPF project creation.

The pack URI in WPF