启用OwinStartup致ASP.NET WebForm应用抛出FileLoadException求助

基于.NET Framework 4.8的ASP.NET WebForm应用，搭建了独立的SignalR Hub Web应用，控制台客户端可正常连接，但将web.config中owin:AutomaticAppStartup设为true时触发程序集加载错误，设为false则应用正常启动。当前项目中System.Runtime.dll版本为4.8.9，疑似有组件引用了System.Runtime 7.0.0.0但无法定位来源。

相关代码 #

Startup.cs #

[assembly: OwinStartup(typeof(webapp.Startup))]

namespace webapp
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            app.MapSignalR();
        }
    }
}

web.config关键配置 #

<add key="owin:AutomaticAppStartup" value="true" />

错误信息 #

WRN: Comparing the assembly name resulted in the mismatch: Major Version
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.

[FileLoadException: Could not load file or assembly 'System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]

[HttpException (0x80004005): Could not load file or assembly 'System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]

1. 校验NuGet包兼容性 #

确保安装的是适配.NET Framework的SignalR和Owin包：

• 卸载所有针对.NET Core/.NET 5+的包（如Microsoft.AspNetCore.SignalR、Microsoft.AspNetCore.Owin）
• 安装适配.NET Framework的官方包：
  • Microsoft.AspNet.SignalR（核心SignalR包）
  • Microsoft.Owin、Microsoft.Owin.Host.SystemWeb（Owin宿主依赖）

2. 添加程序集绑定重定向 #

在web.config的<runtime>节点下添加绑定重定向，将高版本的System.Runtime映射到当前项目的4.8.9版本：

<runtime>
  <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
    <dependentAssembly>
      <assemblyIdentity name="System.Runtime" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
      <bindingRedirect oldVersion="0.0.0.0-7.0.0.0" newVersion="4.8.9.0" />
    </dependentAssembly>
  </assemblyBinding>
</runtime>

3. 清理并重建项目 #

• 删除项目根目录下的bin和obj文件夹
• 清理NuGet缓存：在Visual Studio中依次点击「工具」→「NuGet包管理器」→「包管理器设置」→「清除所有NuGet缓存」
• 重新还原NuGet包并编译项目

内容的提问来源于stack exchange，提问作者waynemodz