ASP.NET server controls

The server control

Controls are small blocks of functionality in the graphical user interface, including text boxes, buttons, check boxes, list boxes, labels, and many other tools. With these tools, users can enter data, make choices, and indicate their preferences.

Controls are also used for structural work such as validation, data access, security assurance, creation of master pages, and data operations.

ASP.NET uses five types of Web controls, which are:

• HTML controls
• HTML server controls
• ASP.NET server controls
• ASP.NET Ajax server control
• User controls and custom controls

ASP.NET server control is the primary control ASP.NET used in the application. These controls can be divided into the following categories:

• Validation Control - Used to validate user input and work by running client scripts.
• Data source controls - Provides the ibility of binding data to different data sources.
• Data View Control - This control is a variety of lists and tables that can display data bound from a data source.
• Personalization Controls - Page personalization based on user information, depending on the user's preferences.
• Landing and security controls - Provides user authentication.
• Master page - provides a consistent layout and interface throughout the application.
• Navigation Controls - Helps the user navigate. For example, menus, tree views, and so on.
• Rich feature controls - Implement special features. Examples: AdRotator, FileUpload, and calendar controls.

The basic syntax for using server controls is:

<asp:controlType  ID ="ControlID" runat="server" Property1=value1  [Property2=value2] />

In addition, Visual Studio has the following features to help produce error-free code:

• Drag and drop controls in the design view.
• Intelligent perception of display and auto-completion features.
• The property window that sets the property value directly.

The property of the server control

Visually enabled server controls ASP.NET the WebControl class and inherit all the properties, events, and methods of that category.

The WebControl class itself and other server controls that do not have visualization are derived from the System.Web.UI.Control class. For example, a PlaceHolder control or an XML control.

ASP.Net server control inherits all the properties, events, and methods of the WebControl and System.Web.UI.Control classes.

The following table shows the properties that are common to all server controls:

The method of the server control

The method of the server control is rendered in the following table:

Let's take a look at a specific server control - a tree view control. T he tree view control belongs to the navigation control. Other navigation controls are: menu controls and SiteMapPath controls.

Add a tree view control to the page. S elect the edit node from the task... Use the tree view node editor to edit each node, as follows:

When the node is successfully created, the following is displayed in the design view:

AutoFormat... Tasks allow you to specify the format of the tree view, as follows:

Add a label control and a text box control to the page and name it lblmessage and txtmessage, respectively.

Write a few lines of code to make sure that when a particular node is selected, the label control displays the node text and the text box displays all the sub-nodes below it, if any. The code for the background file should look like this:

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;

using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

namespace eventdemo {
   public partial class treeviewdemo : System.Web.UI.Page {

      protected void Page_Load(object sender, EventArgs e) { 
         txtmessage.Text = " "; 
      }

      protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e) {

         txtmessage.Text = " "; 
         lblmessage.Text = "Selected node changed to: " + TreeView1.SelectedNode.Text;
         TreeNodeCollection childnodes = TreeView1.SelectedNode.ChildNodes;

         if(childnodes != null) {
            txtmessage.Text = " ";

            foreach (TreeNode t in childnodes) {
               txtmessage.Text += t.Value;
            }
         }
      }
   }
}

By executing the page to see the effect, you will be able to expand and collapse nodes.