在第4和第5行发生长度不能小于零 [英] Length cannot be less than zero error occured at 4th and 5th line

问题描述

1 string userIP = Request.UserHostAddress;

2 string serverIP = Request.ServerVariables [LOCAL_ADDR];

3

4 userIP = userIP.Substring（0，userIP.LastIndexOf（。））;

5 serverIP = serverIP.Substring（1，serverIP.LastIndexOf（。））;

1 string userIP = Request.UserHostAddress;
2 string serverIP = Request.ServerVariables["LOCAL_ADDR"];
3
4 userIP = userIP.Substring(0, userIP.LastIndexOf("."));
5 serverIP = serverIP.Substring(1, serverIP.LastIndexOf("."));

// only redirect to WinLogin.aspx if user is internal & IE
 if (userIP.Equals(serverIP) && Request.Browser.IsBrowser("ie"))
  {
     Server.Transfer("SecondLogin.aspx"");
  }
else
  {
     Server.Transfer("ThirdLogin.aspx"");
  }

推荐答案

userIP和serverIP中包含哪些值。



检查长度是否大于0然后只执行substring语句。

What values coming inside userIP and serverIP.

Put a check if length is greater then 0 then only execute the substring statement.

userIP.Substring（0，userIP.LastIndexOf（ 。））;

LastIndexOf 如果找不到文本则返回-1。



在您的情况下，在 userIP 中找不到'。'并且返回-1。

因此， Substring 失败因为子串（0，-1）没有意义。



设置一些验证条件以确保在执行子字符串之前存在有效的IP值。

userIP.Substring(0, userIP.LastIndexOf("."));
LastIndexOf returns -1 if text is not found.

In your case, a '.' is not being found in userIP and -1 is being returned.
As a result, Substring fails becaause Substring(0, -1) makes no sense.

Put some validation conditions to ensure there is a valid IP value before doing a sub string.

这篇关于在第4和第5行发生长度不能小于零的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！