VB.NET函数作为字符串，将返回假布尔？

Question

我有一个HTTP类，从URL的内容，POST的内容到URL的内容等，然后返回原始的HTML内容。

在函数里面的类检测是否有HTTP错误，如果是这样我想返回false，但是如果我已经声明函数返回一个字符串，这将工作吗？什么我试图做

代码示例（请注意，如果检测到一个HTTP错误代码返回内容&返回FALSE）

Public Function Get_URL(ByVal URL As String) As String 
    Dim Content As String = Nothing 
    Try 
     Dim request As Net.HttpWebRequest = Net.WebRequest.Create(URL) 
     ' Request Settings 
     request.Method = "GET" 
     request.KeepAlive = True 
     request.AllowAutoRedirect = True 
     request.Timeout = MaxTimeout 
     request.CookieContainer = cookies 
     request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/534.24 (KHTML, like Gecko) Chrome/11.0.696.60 Safari/534.24" 
     request.Timeout = 60000 
     request.AllowAutoRedirect = True 
     Dim response As Net.HttpWebResponse = request.GetResponse() 
     If response.StatusCode = Net.HttpStatusCode.OK Then 
      Dim responseStream As IO.StreamReader = New IO.StreamReader(response.GetResponseStream()) 
      Content = responseStream.ReadToEnd() 
     End If 
     response.Close() 
    Catch e As Exception 
     HTTPError = e.Message 
     Return False 
    End Try 
    Return Content 
End Function 

和使用例如：

Dim Content As String = Get_URL("http://www.google.com/") 
If Content = False Then 
    MessageBox.Show("A HTTP Error Occured: " & MyBase.HTTPError) 
    Exit Sub 
End If 

Answer 1

通常在这种类型的场景中，你会抛出一个新的异常并提供更详细的信息，并让异常冒泡到主代码处理的状态（或者让原来的异常冒出来，而不是首先捕获它）。

Catch e As Exception 
    ' wrap the exception with more info as a nested exception 
    Throw New Exception("Error occurred while reading '" + URL + "': " + e.Message, e) 
End Try 

里面的使用例子：

Dim content As String = "" 
Try 
    content = Get_URL("http://www.google.com/") 
Catch e As Exception 
    MessageBox.Show(e.Message) 
    Exit Sub 
End Try