0

I created several user controls - most containing a single web control (text box, drop down, radio button etc) - along with one or more validation controls. The point being to combine control and validation in a single user control.

I created a base class for these user control with some common functionality - setters for several properties of a single web control, specifically CssClass and Style to be set in the control in the ascx.
Eg a single text box with a single required field validator.

Sample code for the base class:

public WebControl ctrl {get; set;}  //allow derived class access to this

public string CssClass
{
  set { ctrl.CssClass = value; }    //allow CssClass to be set in the aspx page
}

Sample code for derived class: (in constructor or control OnInit Event - or ?)

base.ctrl = txt;    //tell the base class which web control to apply common properties to.

public string ErrorMessage
{
    set { val.ErrorMessage = value;}    //this works !
}

Sample code for ascx:

<asp:TextBox ID="txt" Cssclass="input-text-m" maxlength="50" runat="server" />
<asp:RequiredFieldValidator ID="val" runat="server" ControlToValidate="txt" 
    ErrorMessage="">*</asp:RequiredFieldValidator>

Sample code for aspx:

<uc:TextBox ID="ForeName" Cssclass="input-text-m" maxlength="50" 
ErrorMessage="Forename" runat="server"/>

The problem I found was that I couldn't find a way for the derived class to set the base class web control reference before the base classes property setters are called. If I set base.ctrl in the derived class constructor - then the derived class control reference (txt) is still null at this point. If I set base.ctrl in any of the control events - eg OnInit - then this is too late.

So far I have got around the problem by simply not using a base class, and writing the property setter code in the user control class instead, however this means duplication of code, which I was trying to avoid.

Is there a way to inform the base class of the control I want it to set the properties for in advance of them being set - or am I going about things the wrong way...

mearle
  • 3
  • 2

1 Answers1

0

What about calling EnsureChildControls before any get/set operations and including the set operation for ctrl = txt in EnsureChildControls? This is pretty standard practice for a normal servercontrol, I would think it would work for UserControls too.

public string CssClass {   set { EnsureChildControls(); ctrl.CssClass = value; } }

Override EnsureChildControls, leaving in the call to base, and set ctrl = txt; here after the call to base.

More information: http://msdn.microsoft.com/en-us/library/system.web.ui.control.ensurechildcontrols.aspx

Peter
  • 9,643
  • 6
  • 61
  • 108
  • Well, your idea works, though it seems that EnsureChildControls() is not necessary in this case. The important bit was the override idea, which allows the base class property setters to access the derived class control directly at the time it is needed - and by this time, the control reference (txt) is no longer null. I created a virtual property for the control in the base class, and overrode it in the derived class as follows: `code` public virtual WebControl ctrl { get; set; } public override WebControl ctrl { get { return txt; } } `code` And that works a treat ! – mearle Dec 21 '11 at 15:25