“/”应用程序中的服务器错误。

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行 534:        string extension = Path.GetExtension(link); //得到扩展名
行 535:        
行 536:        string pdf_name=link.Replace(extension, ".pdf");
行 537:        return pdf_name;
行 538:    }

[ArgumentException: 字符串的长度不能为零。
参数名: oldValue]
   System.String.ReplaceInternal(String oldValue, String newValue) +0
   System.String.Replace(String oldValue, String newValue) +20
   ASP.<get_pdf_url>d__3a.MoveNext() in d:\wwwroot\spider.wskmn.com\bx\index.aspx:536
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
   System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() +28
   ASP.<error>d__d.MoveNext() in d:\wwwroot\spider.wskmn.com\bx\index.aspx:288
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
   System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() +28
   ASP.<getsource>d__8.MoveNext() in d:\wwwroot\spider.wskmn.com\bx\index.aspx:195
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
   System.Runtime.CompilerServices.TaskAwaiter`1.GetResult() +28
   ASP.<PageLoadAsync>d__0.MoveNext() in d:\wwwroot\spider.wskmn.com\bx\index.aspx:114
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
   System.Web.UI.<ExecuteTasksAsync>d__3.MoveNext() +363
   System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) +99
   System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) +58
   System.Web.UI.<ProcessRequestAsync>d__554.MoveNext() +876