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UWP-webRequest

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Week 7

Request

  1. 使用 HttpClient 访问网络
  2. 提供城市天气查询(json Phrase)
  3. 提供 IP 地址查询(xml Phrase)

Accomplish

使用 HttpClient 访问网络

下面参考 Microsoft UWP Document 提供了利用 HttpClient 通过 网址 url 进行网络访问的代码模板。我们要做的事就三个：

  1. 给函数提供访问的 url 所需的参数；
  2. 替换将要访问的 url
  3. 完成下面的 http response处理代码

函数的返回值可以自行修改。

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private async Task<string> WeatherApi(/*params*/) {
    HttpClient httpClient = new HttpClient();
    var headers = httpClient.DefaultRequestHeaders;

    // The safe way to add a header value is to use the TryParseAdd method
    // and verify the return value is true,
    // especially if the header value is coming from user input.
    string header = "ie";
    if (!headers.UserAgent.TryParseAdd(header)) {
        throw new Exception("Invalid header value: " + header);
    }

    header = "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)";
    if (!headers.UserAgent.TryParseAdd(header)) {
        throw new Exception("Invalid header value: " + header);
    }

    string uri = "url";
    Uri requestUri = new Uri(uri);
    //Send the GET request asynchronously and retrieve the response as a string.
    HttpResponseMessage httpResponse = new HttpResponseMessage();
    string httpResponseBody = "";

    try {
        //Send the GET request
        httpResponse = await httpClient.GetAsync(requestUri);
        httpResponse.EnsureSuccessStatusCode();
        // Set encoding to 'UTF-8'
        Byte[] getByte1 = await httpResponse.Content.ReadAsByteArrayAsync();
        Encoding code1 = Encoding.GetEncoding("UTF-8");
        string result1 = code1.GetString(getByte1, 0, getByte1.Length);
        // Pharse the json data
        JsonReader reader = new JsonTextReader(new StringReader(result1));
        while (reader.Read()) {
            // Do something here with the response data
        }
    } catch (Exception ex) {
        httpResponseBody = "Error: " + ex.HResult.ToString("X") + " Message: " + ex.Message;
    }
    return /*string*/;
}

提供城市天气查询(json Phrase)

下面给出有关于 json phrase 的代码。
这里调用的是中国气象局的api，作为一个年迈的网站，它的查询 url 不支持城市中文名，而应使用城市代码。感谢blouc的贡献，我直接将它洗成 xml 来辅助使用了，具体见代码文件内的 weather.xml 文件。
对于 json 数据的解析，使用 newton 库提供的 json 解析库。

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/* Accomplish the url */
// Get the city code for the api
string code = "101010100";
XmlDocument cityCode = new XmlDocument();
cityCode.LoadXml(System.IO.File.ReadAllText("Weather.xml"));
foreach (IXmlNode node in cityCode.GetElementsByTagName("City")) {
    if ((string)node.Attributes[0].NodeValue == city) {
        code = (string)node.Attributes[2].NodeValue;
    }
}
string uri = "http://www.weather.com.cn/data/sk/" + code + ".html";

/* Json Phrase Code for httpResponse data */

//Send the GET request
httpResponse = await httpClient.GetAsync(requestUri);
httpResponse.EnsureSuccessStatusCode();
// Set encoding to 'UTF-8'
Byte[] getByte1 = await httpResponse.Content.ReadAsByteArrayAsync();
Encoding code1 = Encoding.GetEncoding("UTF-8");
string result1 = code1.GetString(getByte1, 0, getByte1.Length);
// Phrase the json data
JsonReader reader = new JsonTextReader(new StringReader(result1));
while (reader.Read()) {
    if ((String)reader.Value == "city") {
        weather += "城市: ";
        reader.Read();
        if (reader.Value != null)
            weather += reader.Value + "\n";
    } else if ((String)reader.Value == "temp") {
        weather += "温度: ";
        reader.Read();
        if (reader.Value != null)
            weather += reader.Value + "℃\n";
    } else if ((String)reader.Value == "WD") {
        weather += "风向: ";
        reader.Read();
        if (reader.Value != null)
            weather += reader.Value + "\n";
    } else if ((String)reader.Value == "WS") {
        weather += "风速: ";
        reader.Read();
        if (reader.Value != null)
            weather += reader.Value + "\n";
    } else if ((String)reader.Value == "SD") {
        weather += "相对湿度: ";
        reader.Read();
        if (reader.Value != null)
            weather += reader.Value + "\n";
    } else if ((String)reader.Value == "time") {
        weather += "时间: ";
        reader.Read();
        if (reader.Value != null)
            weather += reader.Value + "\n";
    }
}

提供 IP 地址查询(xml Phrase)

调用网络服务的代码与天气查询的是一致的，只是更换了 url 网址与下面的 httpResponse 处理代码。
这里返回了 xml 数据，我们利用官方提供的

库进行解析。
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```cs
Byte[] getByte = await httpResponse.Content.ReadAsByteArrayAsync();
Encoding code = Encoding.GetEncoding("UTF-8");
string result = code.GetString(getByte, 0, getByte.Length);
// Phrase the xml data
XmlDocument document = new XmlDocument();
document.LoadXml(result);

var province = document.GetElementsByTagName("province");
location += "省份: " + province[0].InnerText + "\n";

var city = document.GetElementsByTagName("city");
location += "城市: " + city[0].InnerText + "\n";

var rectangle = document.GetElementsByTagName("rectangle");
var temp = rectangle[0].InnerText.Split(';');
location += "区域:\n\t" + temp[0] + "\n\t" + temp[1] + "\n";

成品图

Query