下载webapi web.config文件的modules节点上加如下图
：
再在win+r cmd 运行如下命令：
如果下面两条命令执行不成功
C:\Windows\Microsoft.NET\Framework\v4.0.30319\aspnet_regiis.exe -i
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet_regiis.exe -i
则使用下列命令
dism /online /enable-feature /featurename:IIS-ISAPIFilter
dism /online /enable-feature /featurename:IIS-ISAPIExtensions
dism /online /enable-feature /featurename:IIS-NetFxExtensibility45
dism /online /enable-feature /featurename:IIS-ASPNET45