如何检查网址是否存在？

问题描述

  Dim  urlexist  As  整数 =  0  
  Dim  urlDoesNotExist 作为 整数 =  0  
 对于 每个行在 TextBox1.Text.Split（Environment.NewLine）
  Dim  url 作为 新系统.Uri（line）
  Dim  req  As  System.Net.WebRequest 
 req = System.Net.WebRequest.Create（url）
  Dim  resp  As  System.Net。 WebResponse 
 尝试 
 resp = req.GetResponse（）
 resp.Close（）
 req = 没什么 
 urlexist = urlexist +  1  
 '  MsgBox（找到网站！） 
  Catch  ex  As  Exception 
 req =  Nothing  
 urlDoesNotExist = urlDoesNotExist +  1  
   MsgBox（未找到网站。检查网址和互联网连接） 
 Button1.Text = urlDoesNotExist +  1  
 返回 
 结束 尝试 
 下一步 
 MsgBox（ 存在是，urlexist） 
 MsgBox（ 不存在是，urlDoesNotExist）
 

我的尝试：



此循环在2之后停止为什么？现在我不知道这里出现了什么问题

解决方案

Dim urlexist As Integer = 0
     Dim urlDoesNotExist As Integer = 0
     For Each line In TextBox1.Text.Split(Environment.NewLine)
         Dim url As New System.Uri(line)
         Dim req As System.Net.WebRequest
         req = System.Net.WebRequest.Create(url)
         Dim resp As System.Net.WebResponse
         Try
             resp = req.GetResponse()
             resp.Close()
             req = Nothing
             urlexist = urlexist + 1
             'MsgBox("Website Found!")
         Catch ex As Exception
             req = Nothing
             urlDoesNotExist = urlDoesNotExist + 1
             '   MsgBox("Website not found. Check the url and internet connection")
             Button1.Text = urlDoesNotExist + 1
             Return
         End Try
     Next
     MsgBox("exist is ", urlexist)
     MsgBox("non-exist is ", urlDoesNotExist)

What I have tried:

this loop stops after 2 why ? now i don't under stand what went wrong in this

解决方案

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