在ASP.NET Core应用程序中使用AspNetCore.Proxy时，可能会遇到复用代理连接时出现错误的问题。通常会收到以下错误消息：

“Cannot reuse proxy connection. The connection with the server was closed.”

解决此问题需要在创建HttpClient实例时，将HttpProxyOptions的MaxConnectionPerServer属性设置为较高的值。以下是代码示例：

services.AddHttpClient("MyService", client => { // set other properties of the client as needed }).ConfigurePrimaryHttpMessageHandler(config => new HttpClientHandler { AllowAutoRedirect = false, UseProxy = true, MaxConnectionsPerServer = 100 // set a higher value here }).AddHttpMessageHandler();

请根据具体情况自行调整MaxConnectionsPerServer属性的值。