ASP.NET Web Api 实践系列（二）Get/Post方式调用Web Api

    本文给出Get/Post方式访问Web Api的帮助方法，对于Put/Delete方式的调用跟Post调用类似。

    一、Web Api调用帮助类

    下面给出Web Api调用帮助类的代码：

using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Web;

namespace TestApi
{
    /// <summary>
    /// WebApi访问帮助类
    /// </summary>
    public class WebApiHepler
    {
        /// <summary>
        /// 生成最终URL
        /// </summary>
        /// <param name="baseUrl">基准URL（不含查询串）</param>
        /// <param name="dictParam">查询参数字典</param>
        /// <returns>最终URL</returns>
        private static string GetLastUrl(string baseUrl, Dictionary<string, string> dictParam)
        {
            var sbUrl = new StringBuilder(baseUrl);
            if (dictParam != null && dictParam.Count > 0)
            {
                sbUrl.Append("?");
                int index = 0;
                foreach (var item in dictParam)
                {
                    sbUrl.Append(string.Format("{0}={1}", item.Key,
                        HttpUtility.UrlEncode(item.Value, Encoding.UTF8)));
                    if (index < dictParam.Count - 1)
                    {
                        sbUrl.Append("&");
                    }
                    index++;
                }
            }
            var url = sbUrl.ToString();
            return url;
        }

        /// <summary>
        /// GET方式调用Web Api
        /// </summary>
        /// <param name="baseUrl">基准URL（不含查询串）</param>
        /// <param name="dictParam">查询参数字典</param>
        /// <param name="result">返回数据（Json格式）</param>
        /// <param name="errMsg">出错信息</param>
        /// <returns>成功与否</returns>
        public static bool Get(string baseUrl, Dictionary<string, string> dictParam, out string result, out string errMsg)
        {
            errMsg = string.Empty;
            result = string.Empty;
            try
            {
                using (var client = new HttpClient())
                {
                    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                    var url = GetLastUrl(baseUrl, dictParam);
                    var tmpResult = client.GetAsync(url).Result;
                    tmpResult.EnsureSuccessStatusCode();
                    result = tmpResult.Content.ReadAsStringAsync().Result;
                    return true;
                }
            }
            catch (Exception ex)
            {
                errMsg = ex.Message;
                return false;
            }
            
        }

        /// <summary>
        /// POST方式调用Web Api
        /// </summary>
        /// <param name="baseUrl">基准URL（不含查询串）</param>
        /// <param name="dictParam">查询参数字典</param>
        /// <param name="parseData">传递实体数据（Json格式）</param>
        /// <param name="result">返回数据（Json格式）</param>
        /// <param name="errMsg">出错信息</param>
        /// <returns>成功与否</returns>
        public static bool Post(string baseUrl, Dictionary<string, string> dictParam, string parseData, out string result, out string errMsg)
        {
            errMsg = string.Empty;
            result = string.Empty;
            try
            {
                using (var client = new HttpClient())
                {
                    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                    var url = GetLastUrl(baseUrl, dictParam);
                    var content = new StringContent(parseData, Encoding.UTF8);
                    content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
                    var tmpResult = client.PostAsync(url, content).Result;
                    tmpResult.EnsureSuccessStatusCode();
                    result = tmpResult.Content.ReadAsStringAsync().Result;
                    return true;
                }
            }
            catch (Exception ex)
            {
                errMsg = ex.Message;
                return false;
            }
        }
    }
}

    二、部分说明

    对以上的代码作部分说明：

• GetLastUrl方法用于根据基准URL和查询参数字典获取最终URL
• client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));这句代码表示希望服务返回Json字符串。
• content.Headers.ContentType = new MediaTypeHeaderValue("application/json"); 表示以Json格式传递实体内容。