.net - 如果从 WebClient 引发，是否应该处理 WebException 中的 WebResponse 引用？

Question

相关问题:WebClient in .Net not releasing socket resources

在调试资源泄漏问题时，我注意到 System.Net.WebException (非一次性类型)包含对 System.Net.WebResponse 的引用(一次性类型)。我想知道在显式处理 WebResponse 时是否应该处理此引用如以下代码段所示。

using (WebClient client = new WebClient())
{
    WebException ex = Assert.Throws<WebException>(() => client.OpenRead(myUri));
    Assert.That(
        ((HttpWebResponse)ex.Response).StatusCode,
        Is.EqualTo(HttpStatusCode.ServiceUnavailable));
}

WebException.WebResponse引用是 WebClient 中现有引用的副本.我还以为会通过WebClient.Dispose处理掉但事实并非如此 WebClient不会覆盖 protected Component.Dispose(bool)基法。事实上，拆解表明WebResponse资源永远不会被处理，而是在不再需要时设置为 null。

public Stream OpenRead(Uri address)
{
    Stream stream2;

    // --- removed for brevity ---

    WebRequest request = null;
    this.ClearWebClientState();
    try
    {
        request = this.m_WebRequest = this.GetWebRequest(this.GetUri(address));
        Stream responseStream = (this.m_WebResponse = this.GetWebResponse(request)).GetResponseStream();

        // --- removed for brevity ---

        stream2 = responseStream;
    }
    catch (Exception exception)
    {

        // --- removed for brevity ---

        AbortRequest(request);
        throw exception;
    }
    finally
    {
        this.CompleteWebClientState();
    }
    return stream2;
}

... 与 ClearWebClientState()如下:

private void ClearWebClientState()
{
    // --- removed for brevity ---

    this.m_WebResponse = null;
    this.m_WebRequest = null;
}

Answer 1

要确保释放 WebResponse 的资源，您可以显式调用 Close 方法。

这是修改后的 ClearWebClientState 方法:

private void ClearWebClientState()
{
    // --- removed for brevity ---
    if ( this.m_WebResponse != null )
        this.m_WebResponse.Close();
    this.m_WebResponse = null;

    this.m_WebRequest = null;
}