My url checker function is hanging application in vb.net - vb.net

Question

Here is vb.net 2008 code is:
Public Function CheckURL(ByVal URL As String) As Boolean
Try
Dim Response As Net.WebResponse = Nothing
Dim WebReq As Net.HttpWebRequest = Net.HttpWebRequest.Create(URL)
Response = WebReq.GetResponse
Response.Close()
Return True
Catch ex As Exception
End Try
End Function
when a url is processing in checking it hangs my application for a while. Is this possible it checks smoothly all url list without hanging my application..
Is there any other fastest way to check urls?
Note: I have about 800 urls in file to check all links a valid by website responce or not.

Answer 1

If an exception occurs, the WebResponse object isn't properly disposed of. This can lead to your app running out of connections. Something like this will work better:
Try
Dim WebReq As Net.HttpWebRequest = Net.HttpWebRequest.Create(URL)
Using Response = WebReq.GetResponse()
Return True
End Using
Catch ex as WebException
Return False
End Try
This using the Using keyword ensures that the response is closed and finalized whenever that block exits.
If it's the server itself that's taking awhile to respond, look into the BeginGetResponse method on the HttpWebRequest. Check MSDN for a sample on how to use it. But be warned, that way also lies madness if you are not careful.

Answer 2

The answer is two fold:
Most of the waiting time is due to downloading content you don't need. If you request to only return the header, you will receive substantially less data, which will make your process faster.
As Matt identified, you aren't disposing of your connections, which may slow your process.
Expanding on Matt's answer, do the following:
Try
Dim WebReq As Net.HttpWebRequest = Net.HttpWebRequest.Create(URL)
WebReq.Method = "HEAD" 'This is the important line.
Using Response = WebReq.GetResponse()
Return True
End Using
Catch ex as WebException
Return False
End Try

Answer 3

GetResponse delivers you the whole content to your request. If this is what you want, there's not many room to speed up the request on the client side, since it mostly depends on the URLs server how fast to reply and how much data will be send over. If you just want to check if the URL is valid (or responding at all), it might be better to just ping it.
Keep in mind GetResponse isn't disposed when it runs into an error, so use the code posted by Matt to avoid this.
For your other problem, hanging application, you might avoid this be running this code as a thread.
This works basically like this (from here):
rem at the top of the code
Imports System.Threading
...
rem your event handler, p.e. button click or whatever
trd = New Thread(AddressOf ThreadTask)
trd.IsBackground = True
trd.Start()
rem your code
Private Sub ThreadTask()
dim i as long
Do
i += 1
Thread.Sleep(100)
Loop
End Sub