using var client = new HttpClient();
try
{
    using var stream = await client.GetStreamAsync("https://example.com/data.xml");
    using var xmlReader = XmlReader.Create(stream);

    while (xmlReader.Read())
    {
        if (xmlReader.NodeType == XmlNodeType.Element)
        {
            // 处理元素逻辑
            Console.WriteLine($"读取节点: {xmlReader.Name}");
        }
    }
}
catch (HttpRequestException httpEx)
{
    Console.WriteLine($"网络请求失败: {httpEx.Message}");
}
catch (XmlException xmlEx)
{
    Console.WriteLine($"XML格式错误: {xmlEx.Message}");
}
catch (TaskCanceledException timeoutEx)
{
    Console.WriteLine($"请求超时: {timeoutEx.Message}");
}

var retryPolicy = Policy
    .Handle<HttpRequestException>()
    .Or<TaskCanceledException>()
    .WaitAndRetryAsync(3, attempt => TimeSpan.FromSeconds(Math.Pow(2, attempt)));

await retryPolicy.ExecuteAsync(async () =>
{
    using var stream = await client.GetStreamAsync("https://example.com/data.xml");
    using var xmlReader = XmlReader.Create(stream);

    while (xmlReader.Read())
    {
        if (xmlReader.NodeType == XmlNodeType.Element)
        {
            Console.WriteLine($"节点: {xmlReader.Name}");
        }
    }
});

var requestUri = "https://example.com/stream.xml?since=1720000000";
// 结合上次成功处理的时间或序列号