“/myDataList”应用程序中的服务器错误。
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StartIndex 不能小于 0。参数名: startIndex
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异常详细信息: System.ArgumentOutOfRangeException: StartIndex 不能小于 0。参数名: startIndex

源错误:


行 158：        public String FormatPhotoUrl(String PhotoUrl)
行 159：        {   
行 160：            return(Request.ApplicationPath + "/UpLoads/Photoes/"  + PhotoUrl.Substring(PhotoUrl.LastIndexOf("/"),
行 161：                PhotoUrl.Length - PhotoUrl.LastIndexOf("/")));
行 162：        }
 public String FormatPhotoUrl(String PhotoUrl)
        {   
            return(Request.ApplicationPath + "/UpLoads/Photoes/"  + PhotoUrl.Substring(PhotoUrl.LastIndexOf("/"),
                PhotoUrl.Length - PhotoUrl.LastIndexOf("/")));
        }
<asp:ImageButton ID ="Photoes" Width ="130" Height ="100" Runat ="server" CommandName ="Photo" ImageUrl ='<%#FormatPhotoUrl((String)DataBinder.Eval(Container.DataItem,"PhotoUrl"))%>' CommandArgument ='<%# DataBinder.Eval(Container.DataItem,"PhotoID") %>'>
                                                        </asp:ImageButton>

PhotoUrl.LastIndexOf("/") 这个有可能是 -1
所以在调用它之前应该判断一下.

如何让PhotoUrl.LastIndexOf("/")成正值呀

public String FormatPhotoUrl(String PhotoUrl)
{   
    if(PhotoUrl.LastIndexOf("/") != -1 && PhotoUrl.LastIndexOf("/") < PhotoUrl.Length)
    {
         return(Request.ApplicationPath + "/UpLoads/Photoes/"  + PhotoUrl.Substring(PhotoUrl.LastIndexOf("/"),
     PhotoUrl.Length - PhotoUrl.LastIndexOf("/")));
     }
     else
     {
          return "";
     }
}