c# - 何时调用 WebResponse.Close()

Question

WebResponse response;
try
{                
 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
 request.Timeout = 20000;
 response = request.GetResponse();

 request = (HttpWebRequest)WebRequest.Create(url2);
 response = request.GetResponse();
}
catch(Exception ex)
{
 //do something
}              
finally
{
}

应该在哪里调用 response.Close()？

• 在每次尝试 GetResponse() 之后？

• 在最后一次 GetResponse() 尝试之后？

• 在 finally block 中？

Answer 1

以上都不是。您应该使用 using block :

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Timeout = 20000;
using (WebResponse response = request.GetResponse())
{
    using (var stream = response.GetResponseStream())
    {
        using (var reader = new StreamReader(stream))
        {
            var result = reader.ReadToEnd();
            // Do something with result
        }
    }
}

using block 将确保调用 Dispose 方法，无论是否有异常。 Dispose 将执行与 Close 相同的操作。

using (var d = new DisposableClass()){code;}

相当于:

DisposableClass d = null;
try
{
    d = new DisposableClass();
    code;
}
finally
{
    if (d != null)
        ((IDisposable)d).Dispose();
}