WebAPI传递大数据

约 296 字小于 1 分钟

2019-05-21

在接口中传输图片进制流或BASE64字符串时，使用FormUrlEncodedContent处理参数时，可能会因为参数太长导致异常无效的URL：URL字符串太长

FormUrlEncodedContent:使用application/x-www-form-urlencoded MIME类型编码的名称/值元组的容器，只能传输ContentType:application/x-www-form-urlencoded

实现：

public async Task<string> Post(string url, Dictionary<string, string> param)
        {
            string result="";
            HttpClient click = new HttpClient();
            HttpContent postContent = new FormUrlEncodedContent(param);
            try
            {
                var respMsg = await click.PostAsync(url, postContent);
                respMsg.EnsureSuccessStatusCode();
                result = await respMsg.Content.ReadAsStringAsync();
            }
            catch (HttpRequestException ex)
            {
                result = ex.Message;
            }
            return result;
        }

可是当param太大时 new FormUrlEncodedContent(param)就会抛出异常无效的URL：URL字符串太长

可以用StringContent！

StringContent：基于字符串提供http的内容，传输类型皆可(比如常用的application/x-www-form-urlencoded、application/json、multipart/form-data....)
实现:

public async Task<string> Post(string url, Dictionary<string, string> param)
        {
            string result="";
            HttpClient click = new HttpClient();
            var urlcode = HttpHelp.DicToFormCode(param); //需要把键值对转为urlencoded
            StringContent postContent = new StringContent(urlcode, Encoding.UTF8, "application/x-www-form-urlencoded");
            try
            {
                var respMsg = await click.PostAsync(url, postContent);
                respMsg.EnsureSuccessStatusCode();
                result = await respMsg.Content.ReadAsStringAsync();
            }
            catch (HttpRequestException ex)
            {
                result = ex.Message;
            }
            return result;
        }

 static string DicToFormCode(Dictionary<string, string> param)
        {
            string pc = "";

            foreach (var p in param)
            {
                pc += HttpUtility.UrlEncode(p.Key);
                if (p.Value.GetType() == typeof(object[]))
                    pc += "=" + 	HttpUtility.UrlEncode(JsonConvert.SerializeObject(p.Value)) + "&";
                else
                    pc += "=" + HttpUtility.UrlEncode(p.Value.ToString()) + "&";
            }
            pc = pc.TrimEnd('&');

            return pc;
        }