R – Why don’t Asp.Net controls expose the same events as…

asp.netuser-controls

User control receives same events as Page object and just like Page object also exposes Application, Session, Request and Response objects. I realize UserControl class and Page class both inherit from same TemplateControl class and for that reason share so many of same methods and events.

But then why don’t Asp.Net controls such as TextBox, Label, GridView etc. also derive from same class as Page and UserControl classes – in other words, why would it be a bad idea for controls such as TextBox to have same events ( Page_Load etc ) as UserControl and Page classes do?

Thank you

Best Answer

The single most probable reason for this would be to minimize the serialization size of auto-event-wireup. Everytime you add an event to a handler in WebForms, its persisted across page requests by serializing it into viewstate. By only exposing methods (which are called in tree fashion) that can be overrided, you save yourself from having to serialize those method calls.

Related Solutions

C# – “The Controls collection cannot be modified because the control contains code blocks”

First, start the code block with <%# instead of <%= :

<head id="head1" runat="server">
  <title>My Page</title>
  <link href="css/common.css" rel="stylesheet" type="text/css" />
  <script type="text/javascript" src="<%# ResolveUrl("~/javascript/leesUtils.js") %>"></script>
</head>

This changes the code block from a Response.Write code block to a databinding expression.
Since <%# ... %> databinding expressions aren't code blocks, the CLR won't complain. Then in the code for the master page, you'd add the following:

protected void Page_Load(object sender, EventArgs e)
{
  Page.Header.DataBind();    
}

C# – How to a WPF UserControl inherit a WPF UserControl

Ensure that you have changed the first tag in the xaml to also inherit from your new basetype

<UserControl x:Class="TestDependencyProperty827.DataTypes.DataTypeWholeNumber"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        
    xmlns:s="clr-namespace:System;assembly=mscorlib"
    >

becomes

<myTypes:BaseDataType x:Class="TestDependencyProperty827.DataTypes.DataTypeWholeNumber"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        
    xmlns:s="clr-namespace:System;assembly=mscorlib"
    xmlns:myTypes="clr-namespace:TestDependencyProperty827.DataTypes"
    >

So, to summarise the complete answer including the extra details from the comments below:

The base class should not include a xaml file. Define it in a single (non-partial) cs file and define it to inherit directly from Usercontrol.
Ensure that the subclass inherits from the base class both in the cs code-behind file and in the first tag of the xaml (as shown above).

Best Answer

Related Solutions

C# – “The Controls collection cannot be modified because the control contains code blocks”

C# – How to a WPF UserControl inherit a WPF UserControl

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