ASP.NET control rendering HTML attributes

Question

I have a custom control in an ASP.NET Web Forms project that inherits from System.Web.UI.Control.

I want to add attributes in the markup that to not correspond to properties of that control e.g.

<myControls:Hyperlink runat=server custom-client-side-attr="1"></<myControls:Hyperlink>

The problem I am having is that the exception

Type 'myControls.Hyperlink' does not have a public property named 'custom-client-side-attr'.

I have tried PersistChildren(false), but that does not fix it. It has been a while since I have been in the depths of ASP.NET Web Forms and cannot remember how this is done.

Joe Enos · Accepted Answer · 2013-09-03 17:45:47Z

4

You have to add those in server-code:

hl1.Attributes["custom-client-side-attr"] = "1";

You can still do it in the markup - you'd have to do it prior to the the declaration:

<% hl1.Attributes["custom-client-side-attr"] = "1"; %>
<myControls:Hyperlink ID="hl1" runat=server custom-client-side-attr="1"></<myControls:Hyperlink>

answered Sep 3, 2013 at 17:45

Joe Enos

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3 Comments

J0e3gan Over a year ago

This worked great for me in one case (adding a custom HTML attribute to a table element output by an ASP.NET RadioButtonList). The solution's kludginess is really ASP.NET's fault I think: why ASP.NET does not simply add control attributes in markup without corresponding control properties to the control's Attributes collection is beyond me; and the problem in question also generally indicates something kludgy upstream: this "nasty" gem is handy when you cannot do much about that.

J0e3gan Over a year ago

In another case, no dice applying this fix in markup: System.Web.HttpException: Untrapped Exception: The Controls collection cannot be modified because the control contains code blocks (i.e. <% ... %>).

Joe Enos Over a year ago

Yep, I've never really understood that one - sometimes it didn't make sense why I couldn't modify a control, and sometimes didn't make sense when I could. Some of this ridiculousness is why I was so happy when aspnet MVC came out so I could stick with proper html.

afzalulh · Accepted Answer · 2013-09-03 17:54:27Z

0

If you want an attribute like this, you have to create a property in for the user control. You may use viewstate or hidden control to keep the property persistent. Your code may look something like this:

public string  custom_client_side_attr 
{
    get {
        if (ViewState["custom_client_side_attr"] != null)
        {
            return ViewState["custom_client_side_attr"].ToString();
        }
        return string.Empty;
    }
    set
    {
        ViewState["custom_client_side_attr"] = value;
        //set custom atribute for the hyperlink here
    }
}

And access the property through markup:

<myControls:Hyperlink id="myCustomControl" runat=server custom_client_side_attr="1"></<myControls:Hyperlink>

or in the code:

myCustomControl.custom_client_side_attr="1";

answered Sep 3, 2013 at 17:54

afzalulh

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3 Comments

Pat Long - Munkii Yebee Over a year ago

I cannot add a property because the Hyperlink control is generic. The attributes could be called anything

afzalulh Over a year ago

If you want to access any attribute, it must have to be exposed.

Pat Long - Munkii Yebee Over a year ago

I don't want to access them server side i just want them render on the client. The same think is possible with the standard controls. I just want the attribute "pass-through" to work as the docs say it should

Terry · Accepted Answer · 2019-05-25 14:38:35Z

0

If your custom control derives from WebControl it seems to work as you want.

answered May 25, 2019 at 14:38

Terry

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