c#中通常使用HttpWebRequest进行HTTP网络请求,HttpWebRequest只对Http请求进行了最简单的封装。如果要利用Http协议实现多文件上传,则必须使用POST方法multipart/form-data格式。为了重复使用,我封装了几个方法,实现了多参数文件上传。

添加引用

使用WebRequest需要添加引用System.Web,否则引入出错。

参数封装

方便起见,我把请求参数进行了封装,代码如下:

namespace EasyHttp.Net.Core
{
public class KeyValue
{
public string Key;
public string Value;
public string FilePath;
public string ContentType="*/*";
public KeyValue(string key, string value, string filePath, string contentType)
{
Key = key;
Value = value;
FilePath = filePath;
ContentType = contentType;
}
public KeyValue() { }
public KeyValue(string key, string value, string filePath)
{
Key = key;
Value = value;
FilePath = filePath;
}
public KeyValue(string key, string value)
{
Key = key;
Value = value;
}
}
}

KeyValue代表了广义的参数,可以是普通的键值对,也可以是文件参数。

多文件上传封装

public static void ExecuteMultipartRequest(HttpWebRequest request, List<KeyValue> nvc)
{
Console.WriteLine(request.Headers);
// log.Debug(string.Format("Uploading {0} to {1}", file, url));
string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
HttpWebRequest wr = request;
wr.ContentType = "multipart/form-data; boundary=" + boundary;
wr.Method = "POST";
wr.KeepAlive = true;
wr.Credentials = System.Net.CredentialCache.DefaultCredentials;
using (var rs = wr.GetRequestStream())
{
// 普通参数模板
string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
//带文件的参数模板
string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";
foreach (KeyValue keyValue in nvc)
{
//如果是普通参数
if (keyValue.FilePath == null)
{
rs.Write(boundarybytes, 0, boundarybytes.Length);
string formitem = string.Format(formdataTemplate, keyValue.Key, keyValue.Value);
byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
rs.Write(formitembytes, 0, formitembytes.Length);
}
//如果是文件参数,则上传文件
else
{
rs.Write(boundarybytes, 0, boundarybytes.Length);
string header = string.Format(headerTemplate, keyValue.Key, keyValue.FilePath, keyValue.ContentType);
byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);
rs.Write(headerbytes, 0, headerbytes.Length);
using (var fileStream = new FileStream(keyValue.FilePath, FileMode.Open, FileAccess.Read))
{
byte[] buffer = new byte[4096];
int bytesRead = 0;
long total = 0;
while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
{
rs.Write(buffer, 0, bytesRead);
total += bytesRead;
}
}
}
}
byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
rs.Write(trailer, 0, trailer.Length);
}
}

使用

static void Main(string[] args)
{
var request = WebRequest.Create("http://localhost:8080/test/upload") as HttpWebRequest;
List<KeyValue> keyValues = new List<KeyValue>();
keyValues.Add(new KeyValue("key1","param1"));
keyValues.Add(new KeyValue("key2", "param2"));
keyValues.Add(new KeyValue("file","test1.png","image/png"));
keyValues.Add(new KeyValue("file", "test2.png", "image/png"));
EasyHttp.ExecuteMultipartRequest(request,keyValues);
}