文件下载时出现错误：
System.ArgumentException: 路径中具有非法字符。
在 System.Security.Permissions.FileIOPermission.HasIllegalCharacters(String[] str)
在 System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList)
在 System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, AccessControlActions control, String[] pathList, Boolean checkForDuplicates, Boolean needFullPath)
在 System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)
在 System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share)
在 KeLin.WebSite.PageWap.ResponseFile(String realPath, String fileExt)