Wednesday, May 4, 2005

Hosting a WinControl in an ASP.Net Page

[This was originally posted at]

About a year ago I had the opportunity to write an article for 4GuysFromRolla: Hosting a Windows Control in a Web Form. The article is very straight-forward. It also gets a lot of questions.

The main point is that you can host a Windows UserControl within a web page. There are some highlights from the article, and from what I've learned since then:

  • This requires that the client has the .Net Redistributable installed.
  • Passing data to and from the WinConrol is hard. You can pass data to the control by dynamically recreating the HTML for it (discussed in the article). The best way I know to get data from the control is via an Xml Web Service (not by writing to an Xml File, as I indicated in the article). Writing to a file system could be a security leak, and requires tweaking the security configuration.
  • While the WinControl appears different when embedded in the web page, it can open up a fully-functional win pop-up form. For example, you could add a Timer to the popup form, but it may not work in the WebForm.

The most common problems I get from readers trying to get their WinControl to work:

  • They haven't run the demo, and there's some issue that would be flushed out if they had.
  • It works on their Dev machine, but not someone else's - usually because the other person's machine didn't have the .Net Redistributable installed.
  • They're trying to access some secure resource - if possible I try to avoid this and use web services instead.

I think embedded WinControls are great for toys - for example you want to make a simple online educational game for a school. However, I find that their security and deployment restrictions are cumbersome for an enterprise app.

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