How to register custom server control on ASP.NET page

Question

I have a project and I am trying to register a custom server control (there is no .ascx file) on the page. I am currently using

Class Declaration

namespace MyApp.Controls{
    public class CustomControl: WebControl{
        public string Text
        {
            get
            {
                String s = (String)ViewState["Text"];
                return ((s == null) ? String.Empty : s);
            }
            set
            {
                ViewState["Text"] = value;
            }
        }        
        protected override void RenderContents(HtmlTextWriter output)
        {
            output.Write(Text);
        }
    }
}

On my page,

<%@ Register TagPrefix="myControls" Namespace="MyApp.Controls" %>
<myControls:CustomControl runat="server" Text="What up!" />

I receive a Parser Error, with the message "Unknown server tag 'myControls:CustomControl'."

What am I doing wrong?

I think you need assembly too.

PMC
– PMC

2011-03-11 17:57:37 +00:00
Commented Mar 11, 2011 at 17:57 — PMC
– PMC, Commented Mar 11, 2011 at 17:57

Uwe Keim · Accepted Answer · 2021-11-11 13:05:26Z

47

Well, if this control is in another class library, or even if it's in the same one, it wouldn't be a bad idea to specify control's assembly in @Register:

<%@ Register TagPrefix="myControls" Namespace="MyApp.Controls" Assembly="MyApp" %>
<myControls:CustomControl runat="server" Text="What's up!" />

Clean and rebuild your solution too in order to verify everything is compiled rightly!

edited Nov 11, 2021 at 13:05

Uwe Keim

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answered Mar 11, 2011 at 18:00

Matías Fidemraizer

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4 Comments

Matías Fidemraizer Over a year ago

No problem! Great to know you got it :)

CookieEater Over a year ago

Just wondering, why using Src instead of Assembly does not work? Does this mean I need to compile my source and put the dll in bin folder? Src works with user control.

Matías Fidemraizer Over a year ago

@CookieMonster Well, you don't put the DLL in the bin folder manually.... Do you imagine using Src in order to tell that a regular C# class is the control? And what about the dependencies, where are coming from? Using Src would defeat the point of coding server controls.

Eccentropy Over a year ago

If it still doesn't work, you may need to specify the strong name for the assembly, which you can get by examining the assembly in the GAC. Example: assembly="MyApp, Version=1.0.0.0, Culture=neutral, PublicKeyToken=5499f3feedc0ffee" instead of only assembly="MyApp".

demp · Accepted Answer · 2013-04-30 09:59:51Z

8

If your control will be reused on several pages, you may want to register it in web.config, as one of system.web/pages/controls subelements instead of copy-pasting the same <@Register tag in all affected pages.

web.config:

<system.web>
  <pages ...>
    <controls>
      ...
      <add tagPrefix="myCompany" namespace="MyCompany.Whatever.Controls" assembly="Whatever"/>
    </controls>

thepage.aspx:

<myCompany:ControlClassName ID="TheStuff" runat="server" ... />

answered Apr 30, 2013 at 9:59

demp

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Comments

Oleks · Accepted Answer · 2011-03-11 17:59:33Z

6

You should put your control either under the App_Code folder (in the case if the control not in assembly) or add a reference to assembly where this control is:

<%@ Register TagPrefix="myControls" Namespace="MyApp.Controls"
      Assembly="SomeAssembly" %>

But guessing, your control not under the App_Code folder.

answered Mar 11, 2011 at 17:59

Oleks

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2 Comments

Cosmin Over a year ago

Yup, more details here: msdn.microsoft.com/en-us/library/yhzc935f(v=VS.90).aspx

smartcaveman Over a year ago

I got it to work by adding the Assembly attribute. Placing the code file in App_Code was not necessary

PMC · Accepted Answer · 2011-03-11 18:09:48Z

5

Add an assembly attribute to your register tag

answered Mar 11, 2011 at 18:09

PMC

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