WPF-Why can't I add a WPF window to a library project

Project to add a library project, but cannot join WPF window, WPF Customize control.

Investigated and found it all because of the library project:ProjectTypeGuids

<?xml version="1.0"encoding="Utf-8"? ><project toolsversion="12.0"defaulttargets="Build"xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <import project="$ (Msbuildextensionspath) \$ (msbuildtoolsversion) \microsoft.common.props"condition="Exists (' $ (msbuildextensionspath) \$ (msbuildtoolsversion) \microsoft.common.props ')"/> <PropertyGroup> <configuration condition="' $ ' (Configuration) ' = = '">Debug</Configuration> <platform condition="' $ (Platform) ' = = '">AnyCPU</Platform> <projectguid>{072127c4-0ced-4fa8-8010-7a014e1bdf73}</projectguid> <OutputType>Library</OutputType> <AppDesignerFolder> Properties</appdesignerfolder> <rootnamespace>honeywell.osm.aircraftmanagement</rootnamespace > <AssemblyName>Honeywell.OSM.AircraftManagement</AssemblyName> <targetframeworkversion>v4.0</TargetFrameworkVersion> <FileAlignment> +</FileAlignment><ProjectTypeGuids>{60dc8134-eba5-43b8-bcc9-bb4bc16c2548}; {fae04ec0-301f-11d3-bf4b-00c04f79efbc}</projecttypeguids><TargetFrameworkProfile>Client</TargetFrameworkProfile> </PropertyGroup>

Open the project with notepad++, join the projecttypeguids, everything is normal.