如果你需要跨域上传内容到另外一个域名并且需要获取返回值，使用Asp.Net的作为代理是最好的办法，要是客户端直接提交到iframe中，由于跨域是无法用javascript获取到iframe中返回的内容的。此时需要在自己的网站做一个动态页作为代理，将表单提交到动态页，动态页负责将表单的内容使用WebClient或HttpWebRequest将表单数据再上传到远程服务器，由于在服务器端进行操作，就不存在跨域问题了。
WebClient上传只包含键值对的文本信息示例代码：
string uriString = "http://localhost/login.aspx";
// 创建一个新的 WebClient 实例.
WebClient myWebClient = new WebClient();
string postData = "Username=admin&Password=admin";
// 注意这种拼字符串的ContentType
myWebClient.Headers.Add("Content-Type","application/x-www-form-urlencoded");
// 转化成二进制数组
byte[] byteArray = Encoding.ASCII.GetBytes(postData);
// 上传数据，并获取返回的二进制数据.
byte[] responseArray = myWebClient.UploadData(uriString,"POST",byteArray);
</div>
WebClient上传只包含文件的示例代码：
String uriString = "http://localhost/uploadFile.aspx";
// 创建一个新的 WebClient 实例.
WebClient myWebClient = new WebClient();
string fileName = @"C:/upload.txt";
// 直接上传，并获取返回的二进制数据.
byte[] responseArray = myWebClient.UploadFile(uriString,"POST",fileName);
</div>
对于既包含文件又包含文本键值对信息的示例代码，需要构造表单提交的内容，对于学asp的同学来说，下面的表单提交内容一定不会陌生
-----------------------------7d429871607fe
Content-Disposition: form-data; name="file1"; filename="G:/homepage.txt"
Content-Type: text/plain
：http://www.weikejianghu.com
-----------------------------7d429871607fe
Content-Disposition: form-data; name="filename"
default filename
-----------------------------7d429871607fe--</div>
所以只要拼一个这样的byte[] data数据Post过去，就可以达到同样的效果了。但是一定要注意，对于这种带有文件上传的，其ContentType是不一样的，例如上面的这种，其ContentType为"multipart/form-data; boundary=---------------------------7d429871607fe"。有了ContentType，我们就可以知道boundary(就是上面的"---------------------------7d429871607fe")，知道boundary了我们就可以构造出我们所需要的byte[] data了，最后，不要忘记，把我们构造的ContentType传到WebClient中（例如:webClient.Headers.Add("Content-Type", ContentType);）这样，就可以通过WebClient.UploadData 方法上载文件数据了。
using System;
using System.Web;
using System.IO;
using System.Net;
using System.Text;
using System.Collections;
namespace UploadData.Common
{
public class CreateBytes
{
Encoding encoding = Encoding.UTF8;
public byte[] JoinBytes(ArrayList byteArrays)
{
int length = 0;
int readLength = 0;
// 加上结束边界
string endBoundary = Boundary + "-- ";
byte[] endBoundaryBytes = encoding.GetBytes(endBoundary);
byteArrays.Add(endBoundaryBytes);
foreach (byte[] b in byteArrays)
{
length += b.Length;
}
byte[] bytes = new byte[length];
// 遍历复制
foreach (byte[] b in byteArrays)
{
b.CopyTo(bytes, readLength);
readLength += b.Length;
}
return bytes;
}
public bool UploadData(string uploadUrl, byte[] bytes, out byte[] responseBytes)
{
WebClient webClient = new WebClient();
webClient.Headers.Add("Content-Type", ContentType);
try
{
responseBytes = webClient.UploadData(uploadUrl, bytes);
return true;
}
catch (WebException ex)
{
Stream resp = ex.Response.GetResponseStream();
responseBytes = new byte[ex.Response.ContentLength];
resp.Read(responseBytes, 0, responseBytes.Length);
}
return false;
}
/// 获取普通表单区域二进制数组
public byte[] CreateFieldData(string fieldName, string fieldValue)
{
string textTemplate = Boundary + " Content-Disposition: form-data; name="{0}" {1} ";
string text = String.Format(textTemplate, fieldName, fieldValue);
byte[] bytes = encoding.GetBytes(text);
return bytes;
}
public byte[] CreateFieldData(string fieldName, string filename, string contentType, byte[] fileBytes)
{
string end = " ";
string textTemplate = Boundary + " Content-Disposition: form-data; name="{0}"; filename="{1}" Content-Type: {2} ";
// 头数据
string data = String.Format(textTemplate, fieldName, filename, contentType);
byte[] bytes = encoding.GetBytes(data);
// 尾数据
byte[] endBytes = encoding.GetBytes(end);
// 合成后的数组
byte[] fieldData = new byte[bytes.Length + fileBytes.Length + endBytes.Length];
bytes.CopyTo(fieldData, 0); // 头数据
fileBytes.CopyTo(fieldData, bytes.Length); // 文件的二进制数据
endBytes.CopyTo(fieldData, bytes.Length + fileBytes.Length); //
return fieldData;
}
public string Boundary
{
get
{
string[] bArray, ctArray;
string contentType = ContentType;
ctArray = contentType.Split(';');
if (ctArray[0].Trim().ToLower() == "multipart/form-data")
{
bArray = ctArray[1].Split('=');
return "--" + bArray[1];
}
return null;
}
}
public string ContentType
{
get
{
if (HttpContext.Current == null)
{
return "multipart/form-data; boundary=---------------------------7d5b915500cee";
}
return HttpContext.Current.Request.ContentType;
}
}
}
}
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using UploadData.Common;
using System.IO;
namespace UploadDataWin
{
public class frmUpload : System.Windows.Forms.Form
{
private System.Windows.Forms.Label lblAmigoToken;
private System.Windows.Forms.TextBox txtAmigoToken;
private System.Windows.Forms.Label lblFilename;
private System.Windows.Forms.TextBox txtFilename;
private System.Windows.Forms.Button btnBrowse;
private System.Windows.Forms.TextBox txtFileData;
private System.Windows.Forms.Label lblFileData;
private System.Windows.Forms.Button btnUpload;
private System.Windows.Forms.OpenFileDialog openFileDialog1;
private System.Windows.Forms.TextBox txtResponse;
private System.ComponentModel.Container components = null;
public frmUpload()
{
InitializeComponent();
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose(disposing);
}
private void InitializeComponent()
{
this.lblAmigoToken = new System.Windows.Forms.Label();
this.txtAmigoToken = new System.Windows.Forms.TextBox();
this.lblFilename = new System.Windows.Forms.Label();
this.txtFilename = new System.Windows.Forms.TextBox();
this.btnBrowse = new System.Windows.Fo