Monday, 16 June 2014

ASP.NET - Multi Views

Post By: Hanan Mannan
Contact Number: Pak (+92)-321-59-95-634
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ASP.NET - Multi Views

MultiView and View controls allow you to divide the content of a page into different groups, displaying only one group at a time. Each View control manages one group of content and all the View controls are held together in a MultiView control.

The MultiView control is responsible for displaying one View control at a time. The View displayed is called the active view.

The syntax for a MultiView control is:

<asp:MultView ID= "MultiView1" runat= "server"></asp:MultiView>

The syntax for a View control is:

<asp:View ID= "View1" runat= "server"></asp:View>

However, the View control cannot exist on its own. It would render error if you try to use it stand-alone. It is always used with a Multiview control as:

<asp:MultView ID= "MultiView1" runat= "server">
<asp:View ID= "View1" runat= "server"> </asp:View>
</asp:MultiView>

Properties of the View and MultiView controls

Both the View and MultiView controls are derived from Control class and inherits all its properties, methods and events. The most important property of the View control is Visible property of type Boolean, which sets the visibility of a view.

The MultiView control has the following important properties:

Properties	Description
Views	Collection of View controls within the MultiView
ActiveViewIndex	A zero based index that denotes the active view; if no view is active then the index is -1.

The CommandName attribute of the Button controls associated with the navigation of the MultiView control are associated with some related field of the MultiView control.

For example, if a Button control with CommandName value as NextView is associated with the navigation of the multiview, it automatically navigates to the next view when the button is clicked.

The following table shows the default command names for the above properties:

Properties	Description
NextViewCommandName	NextView
PreviousViewCommandName	PrevView
SwitchViewByIDCommandName	SwitchViewByID
SwitchViewByIndexCommandName	SwitchViewByIndex

The following are the important methods of the MultiView control:

Methods	Description
SetActiveview	Sets the active view
GetActiveview	Retrieves the active view

Every time a view is changed, the page is posted back to the server and a number of events are raised. Some important events are:

Events	Description
ActiveViewChanged	Raised when a view is changed
Activate	Raised by the active view
Deactivate	Raised by the inactive view

Apart from the above mentioned properties, methods and events, multi view control inherits the members of the control and object class.

Example:

The example page has three views. Each view has two button for navigating through the views.

The content file is as follows:

<%@ Page Language="C#" 
         AutoEventWireup="true" 
         CodeBehind="Default.aspx.cs" 
         Inherits="multiviewdemo._Default" %>

<!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>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>

<h2>MultiView and View Controls</h2>
    <asp:DropDownList ID="DropDownList1" 
         runat="server" 
     onselectedindexchanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
<hr />
<asp:MultiView ID="MultiView1" 
         runat="server" 
         ActiveViewIndex="2"
         onactiveviewchanged="MultiView1_ActiveViewChanged" >
<asp:View ID="View1" runat="server">

<h3>This is view 1</h3>
<br />
<asp:Button CommandName="NextView" ID="btnnext1" 
         runat="server" Text = "Go To Next" />

<asp:Button CommandArgument="View3" 
         CommandName="SwitchViewByID" ID="btnlast" 
         runat="server" Text = "Go To Last" />
</asp:View> 
<asp:View ID="View2" runat="server">

<h3>This is view 2</h3>
<asp:Button CommandName="NextView" ID="btnnext2" 
         runat="server" Text = "Go To Next" />
<asp:Button CommandName="PrevView" ID="btnprevious2" 
         runat="server" Text = "Go To Previous View" />
</asp:View> 
<asp:View ID="View3" runat="server">

<h3> This is view 3</h3>
<br />
<asp:Calendar ID="Calender1" runat="server"></asp:Calendar>
<br />
<asp:Button  CommandArgument="0" 
          CommandName="SwitchViewByIndex" ID="btnfirst" 
          runat="server" Text = "Go To Next" />
<asp:Button CommandName="PrevView" ID="btnprevious" 
runat="server" Text = "Go To Previous View" />
</asp:View> 
</asp:MultiView>
</div>
</form>
</body>
</html>

Observe the following:

The MultiView.ActiveViewIndex determines which view will be shown. This is the only view rendered on the page. The default value for the ActiveViewIndex is -1, when no view is shown. Since the ActiveViewIndex is defined as 2 in the example, it shows the third view when executed.

Monday, 16 June 2014