HtmlInputFile.OnPreRender(EventArgs) Method
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Raises the PreRender event for the HtmlInputFile control.
protected:
override void OnPreRender(EventArgs ^ e);protected public:
override void OnPreRender(EventArgs ^ e);protected override void OnPreRender(EventArgs e);protected internal override void OnPreRender(EventArgs e);override this.OnPreRender : EventArgs -> unitProtected Overrides Sub OnPreRender (e As EventArgs)Protected Friend Overrides Sub OnPreRender (e As EventArgs)Parameters
Examples
The following code example demonstrates how to override the OnPreRender method so that a Title attribute is always added to each custom HtmlInputFile control. For this example to work properly, you need to create a directory called Temp on your computer's drive C.
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS.Controls" Assembly="Samples.AspNet.CS" %>
<%@ Page Language="C#" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
void Button1_Click(object Source, EventArgs e)
{
// Make sure a file was submitted.
if (HtmlInputText1.Value == "")
{
Span1.InnerHtml = "Error: You must enter a file name.";
}
// Save the file.
else if (HtmlInputFile1.PostedFile != null)
{
try
{
HtmlInputFile1.PostedFile.SaveAs("c:\\temp\\" + HtmlInputText1.Value);
Span1.InnerHtml = "File uploaded successfully to: <b>c:\\temp\\" +
HtmlInputText1.Value + "</b> on the Web server.";
}
catch (Exception exc)
{
Span1.InnerHtml = "Error saving <b>c:\\temp\\" +
HtmlInputText1.Value + "</b><br />" + exc.ToString() + ".";
}
}
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Custom HtmlInputFile OnPreRender Example</title>
</head>
<body>
<form id="form1" enctype="multipart/form-data"
runat="server">
<h3>Custom HtmlInputFile OnPreRender Example</h3>
Select File to Upload:
<aspSample:CustomHtmlInputFileOnPreRender
id="HtmlInputFile1"
type="file"
runat="server"
name="HtmlInputFile1">
<p>
Save as file name (no path):
<input id="HtmlInputText1"
type="text"
runat="server"
name="Text1" />
</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"
name="Button1" />
</p>
</form>
</body>
</html>
<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.VB.Controls" Assembly="Samples.AspNet.VB" %>
<%@ Page Language="VB" AutoEventWireup="True" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Sub Button1_Click(ByVal source As Object, ByVal e As EventArgs)
' Make sure the file was submitted.
If HtmlInputText1.Value = "" Then
Span1.InnerHtml = "Error: You must enter a file name."
' Save the file
ElseIf Not (HtmlInputFile1.PostedFile Is Nothing) Then
Try
HtmlInputFile1.PostedFile.SaveAs("c:\\temp\\" & HtmlInputText1.Value)
Span1.InnerHtml = "File uploaded successfully to: <b>c:\temp\" _
& HtmlInputText1.Value & "</b> on the Web server."
Catch exc As Exception
Span1.InnerHtml = "Error saving <b>c:\temp\" _
& HtmlInputText1.Value & "</b><br />" _
& exc.ToString() & "."
End Try
End If
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Custom HtmlInputFile OnPreRender Example</title>
</head>
<body>
<form id="form1" enctype="multipart/form-data"
runat="server">
<h3>Custom HtmlInputFile OnPreRender Example</h3>
Select File to Upload:
<aspSample:CustomHtmlInputFileOnPreRender
id="HtmlInputFile1"
type="file"
runat="server"
name="HtmlInputFile1">
<p>
Save as file name (no path):
<input id="HtmlInputText1"
type="text"
runat="server"
name="Text1" />
</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"
name="Button1" />
</p>
</form>
</body>
</html>
using System.Web;
using System.Security.Permissions;
namespace Samples.AspNet.CS.Controls
{
[AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
public sealed class CustomHtmlInputFileOnPreRender : System.Web.UI.HtmlControls.HtmlInputFile
{
protected override void OnPreRender(System.EventArgs e)
{
// Call the base OnPreRender method.
base.OnPreRender(e);
// Add a Title attribute to the HtmlInputFile control.
this.Attributes.Add("title", "Click the Browse button to select a file to upload.");
}
}
}
Imports System.Web
Imports System.Security.Permissions
Namespace Samples.AspNet.VB.Controls
<AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class CustomHtmlInputFileOnPreRender
Inherits System.Web.UI.HtmlControls.HtmlInputFile
Protected Overrides Sub OnPreRender(ByVal e As System.EventArgs)
' Call the base OnPreRender method.
MyBase.OnPreRender(e)
' Add a Title attribute to the HtmlInputFile control.
Me.Attributes.Add("title", "Click the Browse button to select a file to upload.")
End Sub
End Class
End Namespace
Remarks
If no encoding is specified for the Web page's HtmlForm control, the Enctype property is set to "multipart/form-data".
