使用 .NET HttpClient 下载 PDF 文件的DEMO

使用GET方式下载PDF文件

示例代码：

using System;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            System.Net.Http.HttpClient httpClient = new System.Net.Http.HttpClient();
            httpClient.BaseAddress = new Uri("https://dms.esnadexpress.com/");

            System.Net.Http.HttpRequestMessage httpRequestMessage = new System.Net.Http.HttpRequestMessage();
            httpRequestMessage.Method = new System.Net.Http.HttpMethod("GET");
            httpRequestMessage.Headers.Add("context-type", "application/pdf");
            httpRequestMessage.RequestUri = new Uri("https://dms.esnadexpress.com/img/2019-07-16/2/custom_pdf_ESNAD_1563242468479_54981_3223fe36-31c3-4d73-b447-d2c4720046fa.pdf");

            System.Net.Http.HttpResponseMessage httpResponseMessage = httpClient.SendAsync(httpRequestMessage).Result;

            if (httpResponseMessage.StatusCode == System.Net.HttpStatusCode.OK)
            {
                System.IO.Stream stream = httpResponseMessage.Content.ReadAsStreamAsync().Result;
                using (System.IO.FileStream fs = new System.IO.FileStream("e:\\download.pdf",System.IO.FileMode.CreateNew))
                {
                    byte[] buffer = new byte[stream.Length];
                    stream.Read(buffer, 0, buffer.Length);
                    fs.Write(buffer, 0, buffer.Length);
                }
            }
        }
    }
}