如何使用 Windows.Web.Http 中的新 HttpClient 下载图像？

Question

使用Windows.Web.Http.HttpClient 如何下载图像？我想使用这个 HttpClient，因为它可以在可移植类库中使用。

Answer 1

在.net core web api中你可以使用下面的代码

[Route("getProductImage/v1")]
    [HttpGet]
    public async Task<IActionResult> getProductImage(GetProductImageQueryParam parammodel)
    {
        using (HttpClient client = new HttpClient())
        {
            MNimg_URL = MNimg_URL + parammodel.modelname;
            HttpResponseMessage response = await client.GetAsync(MNimg_URL);
            byte[] content = await response.Content.ReadAsByteArrayAsync();
            //return "data:image/png;base64," + Convert.ToBase64String(content);
            return File(content, "image/png", parammodel.modelname);
        }
    }

这里的GetProductImageQueryParam是一个带输入参数的类

Answer 2

public async void downLoadImage(string url)
{
        using (var client = new HttpClient())
        {
            var response = client.GetAsync(url).Result;
            BitmapImage bitmap = new BitmapImage();
            if (response != null && response.StatusCode == HttpStatusCode.OK)
            {
                using (var stream = await response.Content.ReadAsStreamAsync())
                {
                    using (var memStream = new MemoryStream())
                    {
                        await stream.CopyToAsync(memStream);
                        memStream.Position = 0;
                        bitmap.SetSource(memStream.AsRandomAccessStream());
                    }
                }
                HardcodedValues.profilePic = bitmap;
            }
        }
}

Answer 3

为 8.1 - 10 更新。

    public async static Task<BitmapImage> LoadImage(Uri uri)
    {
        BitmapImage bitmapImage = new BitmapImage();

        try
        {
            using (Windows.Web.Http.HttpClient client = new Windows.Web.Http.HttpClient())
            {
                using (var response = await client.GetAsync(uri))
                {
                    response.EnsureSuccessStatusCode();

                    using (MemoryStream inputStream = new MemoryStream())
                    {
                        await inputStream.CopyToAsync(inputStream);
                        bitmapImage.SetSource(inputStream.AsRandomAccessStream());
                    }
                }
            }
            return bitmapImage;
        }
        catch (Exception ex)
        {
            Debug.WriteLine("Failed to load the image: {0}", ex.Message);
        }

        return null;
    }

Answer 4

这是我最终想出的。 Windows.Web.Http.HttpClient 周围的文档并不多，而且很多在线示例都使用了 ReadAllBytesAsync 等旧机制，而此 HttpClient 不提供这些机制。

我应该注意到this question from MSDN 帮助了我很多，所以感谢那个人。正如那边的评论所说，这家伙一定是世界上唯一知道Windows.Web.Http的人！

using System;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Threading.Tasks;
using System.Windows.Media.Imaging;
using Windows.Storage.Streams;
using Windows.Web.Http;

public class ImageLoader
{
    public async static Task<BitmapImage> LoadImage(Uri uri)
    {
        BitmapImage bitmapImage = new BitmapImage();

        try
        {
            using (HttpClient client = new HttpClient())
            {
                using (var response = await client.GetAsync(uri))
                {
                    response.EnsureSuccessStatusCode();

                    using (IInputStream inputStream = await response.Content.ReadAsInputStreamAsync())
                    {
                        bitmapImage.SetSource(inputStream.AsStreamForRead());
                    }
                }
            }
            return bitmapImage;
        }
        catch (Exception ex)
        {
            Debug.WriteLine("Failed to load the image: {0}", ex.Message);
        }

        return null;
    }
}