Why can't I do this in asp.net webforms?

Question

I have one <asp:Image ID="imgBanner1" runat="server"/> control in my aspx page, then in code behind I have this test code:

Image img = new Image();
img.ImageUrl = "~/img/home/home1.jpg";
//...

imgBanner1 = img;  //<--

then when I refresh the page, the src value of the <img> is blank and the picture doesn't appear. I tried to put the snippet in Page_Load, Page_Init, Page_PreInit events but still doesn't work. How can I solve this? I need to asign some custom controls of other clases in my pages... thanks for your answers!.

Edit: It works if I do this:

imgBanner1.ImageUrl = img.ImageUrl;
//...

KV Prajapati · Accepted Answer · 2011-12-31 02:51:02Z

4

If you want to add a control dynamically into a page then add placeholder (or container - Panel etc) control on it and write following code in page_init/page_load. For more info read MSDN article - How to: Add Controls to an ASP.NET Web Page Programmatically?

Image img = new Image();
img.ImageUrl = "~/img/home/home1.jpg";
PlaceHolder1.Controls.Add(img);

ImageUrl is a string property and you have to set string image url.

answered Dec 31, 2011 at 2:51

KV Prajapati

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1 Comment

Jim D'Angelo Over a year ago

+1 Though I'm pretty sure this should be in Page_Init to avoid ViewState issues.

x0n · Accepted Answer · 2011-12-31 02:44:48Z

3

You don't need to instantiate a new Image yourself. This code is generated automatically as a protected field in the page.designer.cs code-behind/beside file. All you need to do is have:

imgBanner1.ImageUrl = "~/img/home/home1.jpg";

in Page_Load and all will be well.

answered Dec 31, 2011 at 2:44

x0n

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3 Comments

Adrianne Over a year ago

yes I know that, but I create another Image control in other class, and one method returns that object, for example one class PageImage : System.Web.UI.WebControls.Image with added properties.

x0n Over a year ago

Now you say that, and edit your question. Sigh. Well, listen to AVD above - add the control dynamically to a placeholder control in Page_Init.

Adrianne Over a year ago

No, I put that since the beginning "I need to asign some custom controls of other clases in my pages" I guess you can check the edit history. btw thanks for your answer.. +1 :)

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