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ASP.NET Adapter Control

, 29 Mar 2012
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Adapt properties like visibility or enabling between ASP.NET Controls.

Introduction

Developing websites with dynamic content can lead to the following requirements:

  • Enable or disable controls dependent on the state of another control
  • Hide or show controls dependent on the visibility of another control 
  • Invert state/visibility dependent on the state/visibility of another control 
The AdapterControl supports these kinds of operations, without the need to change the code behind.

Background  

AdapterControl represents a simple control without a visual representation. The activity area is restricted to the child controls of his parent: 

// ------------------------------------------------------------------------
public class AdapterControl : Control
{

  // ----------------------------------------------------------------------
  public enum AdaptMode
  {
    None,
    Unvaried,
    Inverted,
  } // enum AdaptMode

  // ----------------------------------------------------------------------
  [Themeable( false )]
  public string SourceControl { get; set; }

  // ----------------------------------------------------------------------
  [Themeable( false )]
  public string TargetControl { get; set; }

  // ----------------------------------------------------------------------
  [Themeable( false )]
  public AdaptMode EnabledMode { get; set; }

  // ----------------------------------------------------------------------
  [Themeable( false )]
  public AdaptMode VisibleMode { get; set; }

  // ----------------------------------------------------------------------
  protected override void OnPreRender( EventArgs e )
  {
    base.OnPreRender( e );

    // source
    if ( string.IsNullOrEmpty( SourceControl ) )
    {
      Trace.WriteLine( "AdapterControl: missing source control" );
      return;
    }
    Control source = Parent.FindControl( SourceControl );
    if ( source == null )
    {
      Trace.WriteLine( "AdapterControl: source control '" + SourceControl + "' not found" );
      return;
    }

    // target
    if ( string.IsNullOrEmpty( TargetControl ) )
    {
      Trace.WriteLine( "AdapterControl: missing target control" );
      return;
    }
    Control target = Parent.FindControl( TargetControl );
    if ( target == null )
    {
      Trace.WriteLine( "AdapterControl: target control '" + TargetControl + "' not found" );
      return;
    }

    switch ( VisibleMode )
    {
      case AdaptMode.Unvaried:
        target.Visible = source.Visible;
        break;
      case AdaptMode.Inverted:
        target.Visible = !source.Visible;
        break;
    }

    if ( target.Visible && EnabledMode != AdaptMode.None )
    {
      WebControl sourceWebControl = source as WebControl;
      WebControl targetWebControl = target as WebControl;
      if ( sourceWebControl != null && targetWebControl != null )
      {
        switch ( EnabledMode )
        {
          case AdaptMode.Unvaried:
            targetWebControl.Enabled = sourceWebControl.Enabled;
            break;
          case AdaptMode.Inverted:
            targetWebControl.Enabled = !sourceWebControl.Enabled;
            break;
        }
      }
    }
  } // OnPreRender

} // class AdapterControl 

Using the code

As a prerequisite you have to specify the source and target control using the properties SourceControl and TargetControl:  

<Controls:AdapterControl runat="server" SourceControl="SourceID" TargetControl="TargetID" /> 

The AdapterControl allows you to adapt the enabling state through the property EnabledMode. The visibility can be adapted using the property VisibleMode.   

The adaption will be regulated by the enumeration AdaptMode:

  • None: do not adapt the value (default)
  • Unvaried: adapt the value from the source control one-to-one to the target control
  • Inverted: adapt the inverted value from the source control to the target control 

The following example allows you to switch between two login variations. It demonstrates the EnabledMode controlled by the buttons Enable and Disable and the VisibleMode by the buttons Default Login and Alternate Login

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register TagPrefix="Controls" Namespace="Itenso.Community.AdapterControl.Controls" Assembly="Itenso.Community.AdapterControl.Controls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  <title>Demo AdapterControl</title>
</head>
<body>
  <form id="form1" runat="server">
  <h1>
    Demo AdapterControl</h1>
  <Controls:AdapterControl runat="server" SourceControl="DefaultLoginSettings" TargetControl="AlternateLoginSettings" VisibleMode="Inverted" />

  <Controls:AdapterControl runat="server" SourceControl="DefaultLoginSettings" TargetControl="NameButton" VisibleMode="Inverted" />
  <asp:Button runat="server" ID="NameButton" OnClick="NameMode" Text="Default Login" />
  <Controls:AdapterControl runat="server" SourceControl="DefaultLoginSettings" TargetControl="AlternateLoginButton" VisibleMode="Unvaried" />
  <asp:Button runat="server" ID="AlternateLoginButton" OnClick="AlternateLoginMode" Text="Alternate Login" />
  &nbsp;
  <Controls:AdapterControl runat="server" SourceControl="DefaultLoginSettings" TargetControl="DefaultLoginInfoLabel" VisibleMode="Unvaried" />
  <asp:Label runat="server" ID="DefaultLoginInfoLabel" Text="Current Mode: Default Login" />
  <Controls:AdapterControl runat="server" SourceControl="AlternateLoginSettings" TargetControl="AlternateLoginInfoLabel" VisibleMode="Unvaried" />
  <asp:Label runat="server" ID="AlternateLoginInfoLabel" Text="Current Mode: Alternate Login" />
  <br />
  <br />

  <asp:Panel runat="server" GroupingText="Login">
    <asp:Table runat="server">
      <asp:TableRow runat="server" ID="DefaultLoginSettings">
        <asp:TableCell>
          <asp:Label runat="server" Text="Name:" />
        </asp:TableCell>
        <asp:TableCell>
          <asp:TextBox runat="server" />
          <asp:CheckBox runat="server" Text="Make public" />
        </asp:TableCell>
      </asp:TableRow>
      <asp:TableRow>
        <asp:TableCell />
        <asp:TableCell>
          <Controls:AdapterControl runat="server" SourceControl="DefaultLoginSettings" TargetControl="EnableNameOption" VisibleMode="Unvaried" EnabledMode="Inverted" />
          <asp:Button runat="server" ID="EnableNameOption" OnClick="EnableLogin" Text="Enable" />
          <Controls:AdapterControl runat="server" SourceControl="DefaultLoginSettings" TargetControl="DisableNameOption" VisibleMode="Unvaried" EnabledMode="Unvaried" />
          <asp:Button runat="server" ID="DisableNameOption" OnClick="DisableLogin" Text="Disable" />
        </asp:TableCell>
      </asp:TableRow>
      <asp:TableRow runat="server" ID="AlternateLoginSettings">
        <asp:TableCell>
        <asp:Label runat="server" Text="Name:" />
        </asp:TableCell>
        <asp:TableCell>
          <asp:TextBox runat="server" />
        </asp:TableCell>
      </asp:TableRow>
    </asp:Table>
  </asp:Panel>
  </form>
</body>
</html>

Points of Interest 

  • source and target have to be a child control of the AdapterControl's parent control
  • in case of control dependencies, you have to regard the declaration order
  • the enabling will not be adapted, in case the target control is hidden

History  

29th March 2012: Initial version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Jani Giannoudis
Software Developer (Senior)
Switzerland Switzerland
Jani is Co-founder of Meerazo.com, a free service which allows to share resources like locations, things, persons and their services in a cooperating group of people.

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