项目中添加一个Library 工程，但是却无法加入WPF window, WPF customize control.
调查了一下，发现这一切都由于Library工程中没有：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>512</FileAlignment> <ProjectTypeGuids>{60dc8134-eba5-43b8-bcc9-bb4bc16c2548};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids> <TargetFrameworkProfile>Client</TargetFrameworkProfile> </PropertyGroup>
用Notepad++打开工程，加入ProjectTypeGuids，一切正常了。