Question

是否可以执行HTTP请求并获取Xamarin中的响应正文？因为我在他们的文档中尝试了很多代码示例而且它在我的Android设备上不起作用，所以有一个例外：NameResolutionFailure。

我的代码是：

        Uri uri = new Uri("http://www.google.com");
        string ret = "ERROR";
        try
        {
            using (WebClient webClient = new WebClient())
            {
                //You can set webClient.Headers there
                webClient.Encoding = System.Text.Encoding.UTF8;
                ret = webClient.DownloadString(uri);
                Console.WriteLine("Data: " + ret);
            }
        }
        catch (Exception ex)
        {
            ret = ex.Message;
            Console.WriteLine("Error: " + ret);
        }

我发现当您通过WIFI执行请求时会发生此错误，但是系列性的？

所有肮脏的解决方案，例如“用IP地址替换主机名”都不起作用，我是Xamarin的新手，我对它有不好的印象。

Answer 1

我正在编写一个使用Newtonsoft.Json获取数据的简单示例：

public static async Task<Details> getDetails(string authKey, string AppVersionandBuild)
{

    var response = await JsonWebCall<Details>.GetDirect(
       JsonWebCall<object>.baseURl + "MyApp/GetDetails",
       authKey,
       AppVersionandBuild);

    return response.Item1;
}

这是我的JsonWebCall类

    public class JsonWebCall<T>
{
    public static string baseURl = "http://YourServiceURL/";

     /// <summary>
     /// Gets the client.
     /// </summary>
     /// <returns></returns>
    public static HttpClient GetClient()
    {
        var timeout = new TimeSpan(0, 10, 0);
        var client = new HttpClient(new ModernHttpClient.NativeMessageHandler() );
        // Due to a bug in Xamarin's HttpClient, this value MUST exceed the timeout of the native http client.  
        // The REAL timeout will be the native http client's timeout which will properly throw the timeout exception.
        client.Timeout = timeout.Add(new TimeSpan(0, 1, 0));
        return client;
    }

    /// <summary>
    /// Gets the message.
    /// </summary>
    /// <param name="method">The method.</param>
    /// <param name="url">The URL.</param>
    /// <param name="authkey">The authkey.</param>
    /// <param name="Manufacturer">The manufacturer.</param>
    /// <param name="Model">The model.</param>
    /// <param name="OS">The os.</param>
    /// <param name="OSVersion">The os version.</param>
    /// <param name="UniqueIdentifier">The unique identifier.</param>
    /// <param name="AppVersionandBuild">The application versionand build.</param>
    /// <returns></returns>
    public static HttpRequestMessage GetMessage(HttpMethod method, string url, string authkey, string Manufacturer, string Model, string OS, string OSVersion, string UniqueIdentifier, string AppVersionandBuild)
    {
        var message = new HttpRequestMessage(method, url);

        if (!string.IsNullOrWhiteSpace(authkey))
            message.Headers.Add("X-AUTH-KEY", new List<string>() { authkey });
        if (!string.IsNullOrWhiteSpace(UniqueIdentifier))
            message.Headers.Add("X-DEVICE-ID", new List<string>() { UniqueIdentifier });
        if (!string.IsNullOrWhiteSpace(Model))
            message.Headers.Add("X-DEVICE-MODEL", new List<string>() { Model });
        if (!string.IsNullOrWhiteSpace(Manufacturer))
            message.Headers.Add("X-DEVICE-MFG", new List<string>() { Manufacturer });
        if (!string.IsNullOrWhiteSpace(OSVersion))
            message.Headers.Add("X-OS-VERSION", new List<string>() { OSVersion });
        if (!string.IsNullOrWhiteSpace(OS))
            message.Headers.Add("X-OS-NAME", new List<string>() { OS });
        if (!string.IsNullOrWhiteSpace(AppVersionandBuild))
            message.Headers.Add("X-APP-VERSION", new List<string>() { AppVersionandBuild });
        return message;
    }
    /// <summary>
    /// Get data that is not encapulated in an odata call
    /// </summary>
    /// <param name="url">the url of the service action</param>
    /// <param name="authkey">The authentication key required y the server</param>
    /// <param name="DeviceID">the device id of the device making this service call</param>
    /// <returns></returns>
    public async static Task<Tuple<T>> Get(string url, string authKey, string Manufacturer, string Model, string OS, string OSVersion, string UniqueIdentifier, string AppVersionandBuild)
    {
        var client = GetClient();
        var req = GetMessage(HttpMethod.Get, url, authKey, Manufacturer, Model, OS, OSVersion, UniqueIdentifier, AppVersionandBuild);
        var response = await client.SendAsync(req).ConfigureAwait(false);
        T returnedObject = default(T);
        returnedObject = JsonConvert.DeserializeObject<T>(await response.Content.ReadAsStringAsync().ConfigureAwait(false));

        return new Tuple<T>(returnedObject);
    }
    /// <summary>
    /// Gets the request.
    /// </summary>
    /// <param name="method">The method.</param>
    /// <param name="url">The URL.</param>
    /// <param name="authkey">The authkey.</param>
    /// <param name="AppVersionandBuild">The application versionand build.</param>
    /// <returns></returns>
    public static HttpRequestMessage GetRequest(HttpMethod method, string url, string authkey, string AppVersionandBuild)
    {
        var message = new HttpRequestMessage(method, url);

        if (!string.IsNullOrWhiteSpace(authkey))
            message.Headers.Add("X-AUTH-KEY", new List<string>() { authkey });
        if (!string.IsNullOrWhiteSpace(AppVersionandBuild))
            message.Headers.Add("X-APP-VERSION", new List<string>() { AppVersionandBuild });
        return message;
    }

    /// <summary>
    /// Gets the direct.
    /// </summary>
    /// <param name="url">The URL.</param>
    /// <param name="authKey">The authentication key.</param>
    /// <param name="AppVersionandBuild">The application versionand build.</param>
    /// <returns></returns>
    public async static Task<Tuple<T>> GetDirect(string url, string authKey, string AppVersionandBuild)
    {
        var client = GetClient();
        var req = GetRequest(HttpMethod.Get, url, authKey, AppVersionandBuild);
        var response = await client.SendAsync(req).ConfigureAwait(false);
        T returnedObject = default(T);
        var result = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
        returnedObject = JsonConvert.DeserializeObject<T>(result);
        return new Tuple<T>(returnedObject);
    }   
}

如何修复Xamarin WebClient错误NameResolutionFailure？

1 个答案: