NuGet无法使用XmlnsDefinitionAttribute从程序集中提取元数据

[assembly: XmlnsDefinition("http://schemas.example.com/xaml", "Example.Namespace")]

  <id>Example.Package</id>
 <version>1.0.0</version>
 <title>Example Package</title>
  <authors>Example Author</authors>
  <owners>Example Owner</owners>
  <licenseUrl>http://example.com/license</licenseUrl>
 <projectUrl>http://example.com/project</projectUrl>
  <iconUrl>http://example.com/icon</iconUrl>
 <requireLicenseAcceptance>false</requireLicenseAcceptance>
 <description>Example package description.</description>
 <releaseNotes>Example release notes.</releaseNotes>
  <copyright>Example copyright.</copyright>
  <tags>example tag1 tag2</tags>
 <dependencies>
   <dependency id="Example.Dependency" version="1.0.0" />
  </dependencies>
</metadata>

  <file src="bin\Debug\Example.Package.dll" target="lib\net45" />
</files>