如果你需要跨域上傳內容到另外一個域名并且需要獲取返回值，使用ASP.NET的作為代理是最好的辦法，要是客戶端直接提交到iframe中，由于跨域是無法用Javascript獲取到iframe中返回的內容的。此時需要在自己的網站做一個動態頁作為代理，將表單提交到動態頁，動態頁負責將表單的內容使用WebClient或HttpWebRequest將表單數據再上傳到遠程服務器，由于在服務器端進行操作，就不存在跨域問題了。

WebClient上傳只包含鍵值對的文本信息示例代碼：

復制代碼 代碼如下:
string uriString = "http://localhost/login.ASPx";
// 創建一個新的 WebClient 實例.
WebClient myWebClient = new WebClient();
string postData = "Username=admin&Password=admin";
// 注意這種拼字符串的ContentType
myWebClient.Headers.Add("Content-Type","application/x-www-form-urlencoded");
// 轉化成二進制數組
byte[] byteArray = Encoding.ASCII.GetBytes(postData);
// 上傳數據，并獲取返回的二進制數據.
byte[] responseArray = myWebClient.UploadData(uriString,"POST",byteArray);

WebClient上傳只包含文件的示例代碼：

復制代碼 代碼如下:
String uriString = "http://localhost/uploadFile.ASPx";
// 創建一個新的 WebClient 實例.
WebClient myWebClient = new WebClient();
string fileName = @"C:/upload.txt";
// 直接上傳，并獲取返回的二進制數據.
byte[] responseArray = myWebClient.UploadFile(uriString,"POST",fileName);

　對于既包含文件又包含文本鍵值對信息的示例代碼，需要構造表單提交的內容，對于學ASP的同學來說，下面的表單提交內容一定不會陌生
復制代碼 代碼如下:
-----------------------------7d429871607fe
Content-Disposition: form-data; name="file1"; filename="G:/homepage.txt"
Content-Type: text/plain
腳本之家：http://www.jb51.NET
-----------------------------7d429871607fe
Content-Disposition: form-data; name="filename"
default filename
-----------------------------7d429871607fe--

　　所以只要拼一個這樣的byte[] data數據Post過去，就可以達到同樣的效果了。但是一定要注意，對于這種帶有文件上傳的，其ContentType是不一樣的，例如上面的這種，其ContentType為"multipart/form-data; boundary=---------------------------7d429871607fe"。有了ContentType，我們就可以知道boundary(就是上面的"---------------------------7d429871607fe")，知道boundary了我們就可以構造出我們所需要的byte[] data了，最后，不要忘記，把我們構造的ContentType傳到WebClient中（例如:webClient.Headers.Add("Content-Type", ContentType);）這樣，就可以通過WebClient.UploadData 方法上載文件數據了。

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;      // 加上結束邊界      string endBoundary = Boundary + "-- ";      byte[] endBoundaryBytes = encoding.GetBytes(endBoundary);      byteArrays.Add(endBoundaryBytes);      foreach (byte[] b in byteArrays)      {        length += b.Length;      }      byte[] bytes = new byte[length];      // 遍歷復制      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;    }    /// 獲取普通表單區域二進制數組    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} ";      // 頭數據      string data = String.Format(textTemplate, fieldName, filename, contentType);      byte[] bytes = encoding.GetBytes(data);      // 尾數據      byte[] endBytes = encoding.GetBytes(end);      // 合成后的數組      byte[] fieldData = new byte[bytes.Length + fileBytes.Length + endBytes.Length];      bytes.CopyTo(fieldData, 0); // 頭數據      fileBytes.CopyTo(fieldData, bytes.Length); // 文件的二進制數據      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.Forms.Button();      this.txtFileData = new System.Windows.Forms.TextBox();      this.lblFileData = new System.Windows.Forms.Label();      this.btnUpload = new System.Windows.Forms.Button();      this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();      this.txtResponse = new System.Windows.Forms.TextBox();      this.SuspendLayout();      //       // lblAmigoToken      //       this.lblAmigoToken.Location = new System.Drawing.Point(40, 48);      this.lblAmigoToken.Name = "lblAmigoToken";      this.lblAmigoToken.Size = new System.Drawing.Size(72, 23);      this.lblAmigoToken.TabIndex = 0;      this.lblAmigoToken.Text = "AmigoToken";      //       // txtAmigoToken      //       this.txtAmigoToken.Location = new System.Drawing.Point(120, 48);      this.txtAmigoToken.Name = "txtAmigoToken";      this.txtAmigoToken.Size = new System.Drawing.Size(248, 21);      this.txtAmigoToken.TabIndex = 1;      this.txtAmigoToken.Text = "";      //       // lblFilename      //       this.lblFilename.Location = new System.Drawing.Point(40, 96);      this.lblFilename.Name = "lblFilename";      this.lblFilename.Size = new System.Drawing.Size(80, 23);      this.lblFilename.TabIndex = 2;      this.lblFilename.Text = "Filename";      //       // txtFilename      //       this.txtFilename.Location = new System.Drawing.Point(120, 96);      this.txtFilename.Name = "txtFilename";      this.txtFilename.Size = new System.Drawing.Size(248, 21);      this.txtFilename.TabIndex = 3;      this.txtFilename.Text = "";      //       // btnBrowse      //       this.btnBrowse.Location = new System.Drawing.Point(296, 144);      this.btnBrowse.Name = "btnBrowse";      this.btnBrowse.TabIndex = 4;      this.btnBrowse.Text = "瀏覽";      this.btnBrowse.Click += new System.EventHandler(this.btnBrowse_Click);      //       // txtFileData      //       this.txtFileData.Location = new System.Drawing.Point(120, 144);      this.txtFileData.Name = "txtFileData";      this.txtFileData.Size = new System.Drawing.Size(168, 21);      this.txtFileData.TabIndex = 5;      this.txtFileData.Text = "";      //       // lblFileData      //       this.lblFileData.Location = new System.Drawing.Point(40, 144);      this.lblFileData.Name = "lblFileData";      this.lblFileData.Size = new System.Drawing.Size(72, 23);      this.lblFileData.TabIndex = 6;      this.lblFileData.Text = "FileData";      //       // btnUpload      //       this.btnUpload.Location = new System.Drawing.Point(48, 184);      this.btnUpload.Name = "btnUpload";      this.btnUpload.TabIndex = 7;      this.btnUpload.Text = "Upload";      this.btnUpload.Click += new System.EventHandler(this.btnUpload_Click);      //       // txtResponse      //       this.txtResponse.Location = new System.Drawing.Point(136, 184);      this.txtResponse.Multiline = true;      this.txtResponse.Name = "txtResponse";      this.txtResponse.Size = new System.Drawing.Size(248, 72);      this.txtResponse.TabIndex = 8;      this.txtResponse.Text = "";      //       // frmUpload      //       this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);      this.ClientSize = new System.Drawing.Size(400, 269);      this.Controls.Add(this.txtResponse);      this.Controls.Add(this.btnUpload);      this.Controls.Add(this.lblFileData);      this.Controls.Add(this.txtFileData);      this.Controls.Add(this.btnBrowse);      this.Controls.Add(this.txtFilename);      this.Controls.Add(this.lblFilename);      this.Controls.Add(this.txtAmigoToken);      this.Controls.Add(this.lblAmigoToken);      this.Name = "frmUpload";      this.Text = "frmUpload";      this.ResumeLayout(false);    }    [STAThread]    static void Main()    {      Application.Run(new frmUpload());    }    private void btnUpload_Click(object sender, System.EventArgs e)    {      // 非空檢驗      if (txtAmigoToken.Text.Trim() == "" || txtFilename.Text == "" || txtFileData.Text.Trim() == "")      {        MessageBox.Show("Please fill data");        return;      }      // 所要上傳的文件路徑      string path = txtFileData.Text.Trim();      // 檢查文件是否存在      if (!File.Exists(path))      {        MessageBox.Show("{0} does not exist!", path);        return;      }      // 讀文件流      FileStream fs = new FileStream(path, FileMode.Open,        FileAccess.Read, FileShare.Read);      // 這部分需要完善      string ContentType = "application/octet-stream";      byte[] fileBytes = new byte[fs.Length];      fs.Read(fileBytes, 0, Convert.ToInt32(fs.Length));      // 生成需要上傳的二進制數組      CreateBytes cb = new CreateBytes();      // 所有表單數據      ArrayList bytesArray = new ArrayList();      // 普通表單      bytesArray.Add(cb.CreateFieldData("FileName", txtFilename.Text));      bytesArray.Add(cb.CreateFieldData("AmigoToken", txtAmigoToken.Text));      // 文件表單      bytesArray.Add(cb.CreateFieldData("FileData", path                        , ContentType, fileBytes));      // 合成所有表單并生成二進制數組      byte[] bytes = cb.JoinBytes(bytesArray);      // 返回的內容      byte[] responseBytes;      // 上傳到指定Url      bool uploaded = cb.UploadData("http://localhost/UploadData/UploadAvatar.ASPx", bytes, out responseBytes);      // 將返回的內容輸出到文件      using (FileStream file = new FileStream(@"c: esponse.text", FileMode.Create, FileAccess.Write, FileShare.Read))      {        file.Write(responseBytes, 0, responseBytes.Length);      }      txtResponse.Text = System.Text.Encoding.UTF8.GetString(responseBytes);    }    private void btnBrowse_Click(object sender, System.EventArgs e)    {      if (openFileDialog1.ShowDialog() == DialogResult.OK)      {        txtFileData.Text = openFileDialog1.FileName;      }    }  }}

AspNet技術：Asp.Net模擬表單提交數據和上傳文件的實現代碼，轉載需保留來源！

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