could not load type ‘xxx version=xxxx’系列的解决方法

背景：在使用nuget辅助开发，在部署的过程中，经常会遇到类似：could not load type ‘xxx version=xxxx’的问题，检查了bin文件夹，发现程序集是存在的，然后万分纠结，经过百度无数资料，终于找到解决方法。

原因分析：程序集之间存在各自的依赖项，由于一个同名的程序集只能引用一次，并且程序集有各种各样的版本，如果依赖项的版本比较低，而自己引用的版本比较高的话就会引发这个错误。打个比方：A.dll存在一个依赖项B.dll，版本是1.0.0.0；而在我的项目中，引用了B.dll，但是版本号是：2.0.0.0；这时候就会引发上面所说的错误。

解决办法：在web.config配置文件里面配置一下Runtime节点即可，如下：

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Practices.EnterpriseLibrary.Common" culture="neutral" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Practices.EnterpriseLibrary.Logging" culture="neutral" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Practices.ServiceLocation" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-1.2.0.0" newVersion="1.2.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Practices.Unity" culture="neutral" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.5.0.0" newVersion="3.5.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Practices.Unity.Configuration" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.5.0.0" newVersion="3.5.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Practices.Unity.Interception" culture="neutral" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.5.0.0" newVersion="3.5.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Http" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" publicKeyToken="30ad4fe6b2a6aeed" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="MongoDB.Driver" publicKeyToken="f686731cfb9cc103" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-1.9.2.235" newVersion="1.9.2.235" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="MongoDB.Bson" publicKeyToken="f686731cfb9cc103" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-1.9.2.235" newVersion="1.9.2.235" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Razor" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="AutoMapper" publicKeyToken="be96cd2c38ef1005" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.3.1.0" newVersion="3.3.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-1.5.2.14234" newVersion="1.5.2.14234" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Net.Http.Formatting" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Http.WebHost" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>

其中，在dependentAssembly节点下的assemblyIdentity里面配置对应的程序集名称，token以及oldversion以及newversion；需要说明一下的是，newVersion必须是引用的程序集版本，如果新版以及旧版不存在兼容性问题，问题一般都会迎刃而解~~