Question

我有一个HTTP类，它从URL获取内容，POST的内容到URL等，然后返回原始HTML内容。

在类的内部函数中，它检测是否存在HTTP错误，如果是，我想返回false，但是如果我声明函数返回一个字符串，这会有效吗？

我正在尝试做的代码示例（如果检测到HTTP错误代码，请注意返回内容＆amp;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

用法示例：

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

通常在这种情况下，您会抛出一个包含更多详细信息的新异常，并让异常冒泡到主代码处理（或者让原始异常冒泡而不首先捕获它）。

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

在使用示例中：

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

VB.NET函数为String，返回False是否为布尔值？

1 个答案: