1.找到的程序集与引用的不匹配
solve:webconfig中添加
<dependentAssembly>
<assemblyIdentity name="System.Net.Http.Formatting" publicKeyToken="31bf3856ad364e35" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-5.2.0.0" newVersion="5.2.0.0" />
</dependentAssembly>
原文：http://www.cnblogs.com/sunzgod/p/6483858.html