c# - 你调用的对象是空的？

Question

我写了这些行，但我有 NullReferenceException。请帮我解决一下!

string FullPath = TempPath + FileName;
System.Drawing.Image Adimg = null;
Adimg = System.Drawing.Image.FromFile(MapPath(FullPath));

我将这些行放在一个 Public bool 方法中，TempPath 是类属性，FileName 是该方法的输入。

exception Detail:
System.NullReferenceException was unhandled by user code
  Message="Object reference not set to an instance of an object."
  Source="System.Web"
  StackTrace:
       at System.Web.UI.Page.MapPath(String virtualPath)
       at FileIO.HasValidAttributes(String FileName) in g:\MyProjects\ASP.net Projects\ADBridge\adengine2\App_Code\FileIO.cs:line 44
       at UploadPage.<Page_Load>b__0(Object sender1, EventArgs e1) in g:\MyProjects\ASP.net Projects\ADBridge\adengine2\UploadPage.aspx.cs:line 29
       at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
       at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
  InnerException: 

我没有时间!

Answer 1

尝试在 Server 对象上调用 MapPath:

HttpContext.Current.Server.MapPath(FullPath)