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HtmlInputFile Class

Allows programmatic access to the HTML <input type= file> element on the server.

Namespace: System.Web.UI.HtmlControls
Assembly: System.Web (in system.web.dll)

[ValidationPropertyAttribute("Value")] 
public class HtmlInputFile : HtmlInputControl, IPostBackDataHandler
/** @attribute ValidationPropertyAttribute("Value") */ 
public class HtmlInputFile extends HtmlInputControl implements IPostBackDataHandler
ValidationPropertyAttribute("Value") 
public class HtmlInputFile extends HtmlInputControl implements IPostBackDataHandler

Use the HtmlInputFile server control to handle uploading binary or text files from a browser client to the server. File upload works with Microsoft Internet Explorer version 3.02 or later.

NoteNote

The Enctype property of an HtmlForm control must be set to "multipart/form-data" for this control to work properly.

To specify the file to upload, enter the full path to the file (for example, "C:\MyFiles\Test.txt") in the text box of the control. You can also select the file by clicking the Browse button and then locating it in the Choose file dialog box.

The HtmlInputFile control does not have a built-in way to post back to the server. To upload the file to the server, use the SaveAs method of the System.Web.HttpPostedFile object contained in the PostedFile property. This operation is usually done in an event-handling method, such as for a button click.

NoteNote

When you use the SaveAs method of the HttpPostedFile class, make sure to specify a rooted path (for example, "C:\MyFiles\Test.txt"). The behavior of the SaveAs method can be specified in the httpRuntime Element (ASP.NET Settings Schema) configuration section with the requireRootedSaveAsPath attribute. The default value of this attribute is true. If you set this attribute to false, then using the SaveAs method with no path specified will attempt to place the file in the systemroot \system32\inetsrv directory. By default, this directory is write-protected; therefore, the file can not be saved there. Make sure to provide write permission for the account used by ASP.NET for the directory where you want to store the file.

When uploading large files, use the maxRequestLength attribute of the httpRuntime Element (ASP.NET Settings Schema) element to increase the maximum allowable file size. A DNS error is generated in the browser when the file exceeds the specified size. You might also receive the following error message when uploading large files:

aspnet_wp.exe (PID: 1520) was recycled because memory consumption exceeded 460 MB (60 percent of available RAM).

If you encounter this error message, increase the value of the memoryLimit attribute in the processModel Element (ASP.NET Settings Schema) element of the Machine.config file.

For a list of initial property values for an instance of HtmlInputFile, see the HtmlInputFile constructor.

The following code example demonstrates how to use the HtmlInputFile control to create a simple file upload scenario. For this example to work properly, you need to create a directory called Temp on your computer's drive C.

<%@ Page Language="C#" AutoEventWireup="True" %>

<script runat="server">
 
  void Button1_Click(object Source, EventArgs e)
  {

    if (Text1.Value == "")
    {
      Span1.InnerHtml = "Error: You must enter a file name.";
      return;
    }

    if (File1.PostedFile.ContentLength > 0)
    {
      try
      {
        File1.PostedFile.SaveAs("c:\\temp\\" + Text1.Value);
        Span1.InnerHtml = "File uploaded successfully to <b>c:\\temp\\" +
                           Text1.Value + "</b> on the Web server.";
      }
      catch (Exception exc)
      {
        Span1.InnerHtml = "Error saving file <b>c:\\temp\\" +
                           Text1.Value + "</b><br>" + exc.ToString() + ".";
      }
    }
  }
 
</script>

<html>
  <head>
    <title>HtmlInputFile Example</title>
  </head>
 <body>
 
    <h3>HtmlInputFile Example</h3>
 
    <form enctype="multipart/form-data" 
          runat="server">
       
       Select File to Upload: 
       <input id="File1" 
              type="file" 
              runat="server">
 
       <p>
       Save as file name (no path): 
       <input id="Text1" 
              type="text" 
              runat="server">

       </p>
       <p>
       <span id=Span1 
             style="font: 8pt verdana;" 
             runat="server" />
 
       </p>
       <p>
       <input type=button 
              id="Button1" 
              value="Upload" 
              onserverclick="Button1_Click" 
              runat="server">

       </p>
 
    </form>
 
 </body>
 </html>

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

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