Uploading files

Jan 15 2006

Uploading files

While this article is placed in the upload subsection, it might not be the best place for ot. Because it's not a regular "how-to-upload- files-with-ASP.NET" article.

I might write such an article in the future but this is dealning with a problem you might encounter when using some sort of template-system on your site. I mean basically, all requests goes to a single ASPX page, such as default.aspx and depending on the context (for example sent in by a request variable) you load different user controls (ASCX) files.

For example:
default.aspx?page=start - might show start page
default.aspx?page=clientupload - might show a page when the client could upload a file to your server

Now, back to file upload. To upload a file you need to do two things:
1. Throw in a input type=file control



<INPUT class=textbox id=File1 type=file name=fileUploaded1 runat="server">

2. Set your forms enctype to multipart/form-data

<form enctype="multipart/form-data" runat="server">

Now what's the problem? Well some people might argue that it's no problem at all but the fact is that since you only have one single default.aspx file the form:s type will be always be multipart/form-data - even for the "start"-page. I won't get into that discussion but simple show you how to fix it

Lets say that page=start loads the ucStart.ascx user control. And page=ucClientUpload loads ucClientUpload.ascx

First remove the enctype="multipart/form-data" from the default.aspx form and open up ucClientUpload.ascx

What we are gonna do is from within ucClientUpload.ascx change the form enctype attribute:



protected void EnsureEncType() 
{ 
	System.Web.UI.Control oParent = Parent; 
	while( oParent != null && oParent.GetType() != typeof( System.Web.UI.HtmlControls.HtmlForm ) && oParent.GetType().FullName != "System.Web.UI.Page" ) 
	{ 
		oParent = oParent.Parent; 
	} 
	System.Web.UI.HtmlControls.HtmlForm oForm = oParent as System.Web.UI.HtmlControls.HtmlForm; 
	if ( oForm != null ) 
	oForm.Enctype = "multipart/form-data"; 
}

And then just call EnsureEncType() from your Page_Load function. There you have it. Forms enctype set from within a usercontrol.

I'll be honest with you and say I didn't find out this myself, but it has been in my "toolbox" for quite a while and now when writing this article I was trying to look up who did it, but came up with a lot of chinese pages when googling. Anyway, just saying that so you understand that I don't take any credit for the solution, just trying to spread it.

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Uploading files