名称空间'System.Net'中不存在类型或命名空间名称'Http'(您是否缺少程序集引用？)

Question

我试图在复数视频中关注这个例子

https://app.pluralsight.com/player?course=aspdotnet-5-ef7-bootstrap-angular-web-app&author=shawn-wildermuth&name=aspdotnet-5-ef7-bootstrap-angular-web-app-m7&clip=8&mode=生活&开始= 2

当我试图完成Api添加坐标时,我遇到了错误:

名称空间'System.Net'中不存在类型或命名空间名称'Http'(您是否缺少程序集引用？)

这发生在以下类中:

using Microsoft.Extensions.Logging;
using System.Net;
using System.Threading.Tasks;
using Newtonsoft.Json.Linq;
using System.Net.Http;

namespace Moran.Services
{
    public class CoordService
    {
        private ILogger<CoordService> _logger;

        public CoordService(ILogger<CoordService> logger)
        {
            _logger = logger;
        }

        public async Task<CoordServiceResult> Lookup(string location)
        {
            var result = new CoordServiceResult()
            {
                Success = false,
                Message = "Undetermined failures while looking up coordinates"
            };
            //Lookup Coordinates
            var bingKey = Startup.Configuration["AppSettings:BingKey"];
            var encodedName = WebUtility.UrlEncode(location);
            var url = $"http://dev.virtualearth.net/REST/v1/Locations?q={encodedName}&key={bingKey}";

            var client = new HttpClient();

            var json = await client.GetStringAsync(url);

            // Read out the results
            // Fragile, might need to change if the Bing API changes
            var results = JObject.Parse(json);
            var resources = results["resourceSets"][0]["resources"];
            if (!resources.HasValues)
            {
                result.Message = $"Could not find '{location}' as a location";
            }
            else
            {
                var confidence = (string)resources[0]["confidence"];
                if (confidence != "High")
                {
                    result.Message = $"Could not find a confident match for '{location}' as a location";
                }
                else
                {
                    var coords = resources[0]["geocodePoints"][0]["coordinates"];
                    result.Latitude = (double)coords[0];
                    result.Longitude = (double)coords[1];
                    result.Success = true;
                    result.Message = "Success";
                }
            }
            return result;
        }
    }
}

当我尝试添加时会发生这种情况

var client = new HttpClient();

任何想法为什么会这样？

我找不到任何理由为什么它不编译....

Answer 1

HttpClientclass驻留在System.Net.Http名称空间中,它位于System.Net.Http.dll.要在ASP.NET 5项目中使用此类,您需要添加System.Net.Http到文件"dependencies"中的json数据部分 project.json

  "dependencies": {    
    "Microsoft.AspNet.Diagnostics": "1.0.0-beta5",
    "Microsoft.AspNet.Mvc": "6.0.0-beta5",
    "Microsoft.AspNet.Mvc.TagHelpers": "6.0.0-beta5",
    "Microsoft.AspNet.Server.IIS": "1.0.0-beta5",
    "Microsoft.AspNet.Server.WebListener": "1.0.0-beta5",
    "Microsoft.AspNet.StaticFiles": "1.0.0-beta5",
    "Microsoft.AspNet.Tooling.Razor": "1.0.0-beta5",
    "Microsoft.Framework.Configuration.Json": "1.0.0-beta5",
    "Microsoft.Framework.Logging": "1.0.0-beta5",
    "Microsoft.Framework.Logging.Console": "1.0.0-beta5",

    "System.Net.Http": "4.0.1-beta-23409"

  },

4.0.1-beta-23409是撰写本文时的最新版本.Visual Studio intellisense将为您提供多个可用版本,您可以选择最新/稳定版本.

进行此更改后,当您保存文件时,它将执行dnu恢复(通常会根据需要下载必要的软件包)并添加对System.Net.Http程序集的引用.您可以在类中添加using语句并开始使用HttpClient类.

using System;
using System.Net.Http;
public class SomeClass
{
  public void SomeMethod()
  {
     var client = new HttpClient();
  }
}