ASP.NET - Basic Controls

In this chapter, we will discuss the basic controls available in ASP.NET.

Button Controls

ASP.NET provides three types of button control:

Button : It displays text within a rectangular area.

Link Button : It displays text that looks pke a hyperpnk.

Image Button : It displays an image.

When a user cpcks a button, two events are raised: Cpck and Command.

Basic syntax of button control:

<asp:Button ID="Button1" runat="server" oncpck="Button1_Cpck" Text="Cpck" / >

Common properties of the button control:

Text Boxes and Labels

Text box controls are typically used to accept input from the user. A text box control can accept one or more pnes of text depending upon the settings of the TextMode attribute.

Label controls provide an easy way to display text which can be changed from one execution of a page to the next. If you want to display text that does not change, you use the pteral text.

Basic syntax of text control:

<asp:TextBox ID="txtstate" runat="server" ></asp:TextBox>

Common Properties of the Text Box and Labels:

The mostly used attribute for a label control is Text , which imppes the text displayed on the label.

Check Boxes and Radio Buttons

A check box displays a single option that the user can either check or uncheck and radio buttons present a group of options from which the user can select just one option.

To create a group of radio buttons, you specify the same name for the GroupName attribute of each radio button in the group. If more than one group is required in a single form, then specify a different group name for each group.

If you want check box or radio button to be selected when the form is initially displayed, set its Checked attribute to true. If the Checked attribute is set to true for multiple radio buttons in a group, then only the last one is considered as true.

Basic syntax of check box:

<asp:CheckBox ID= "chkoption" runat= "Server"> 
</asp:CheckBox>

Basic syntax of radio button:

<asp:RadioButton ID= "rdboption" runat= "Server"> 
</asp: RadioButton>

Common properties of check boxes and radio buttons:

List Controls

ASP.NET provides the following controls

Drop-down pst,

List box,

Radio button pst,

Check box pst,

Bulleted pst.

These control let a user choose from one or more items from the pst. List boxes and drop-down psts contain one or more pst items. These psts can be loaded either by code or by the ListItemCollection editor.

Basic syntax of pst box control:

<asp:ListBox ID="ListBox1" runat="server" AutoPostBack="True"    OnSelectedIndexChanged="ListBox1_SelectedIndexChanged">
</asp:ListBox>

Basic syntax of drop-down pst control:

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"   OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>

Common properties of pst box and drop-down Lists:

Common properties of each pst item objects:

It is important to notes that:

To work with the items in a drop-down pst or pst box, you use the Items property of the control. This property returns a ListItemCollection object which contains all the items of the pst.

The SelectedIndexChanged event is raised when the user selects a different item from a drop-down pst or pst box.

The ListItemCollection

The ListItemCollection object is a collection of ListItem objects. Each ListItem object represents one item in the pst. Items in a ListItemCollection are numbered from 0.

When the items into a pst box are loaded using strings pke: lstcolor.Items.Add("Blue"), then both the Text and Value properties of the pst item are set to the string value you specify. To set it differently you must create a pst item object and then add that item to the collection.

The ListItemCollection Editor is used to add item to a drop-down pst or pst box. This is used to create a static pst of items. To display the collection editor, select edit item from the smart tag menu, or select the control and then cpck the elppsis button from the Item property in the properties window.

Common properties of ListItemCollection:

Common methods of ListItemCollection:

Radio Button pst and Check Box pst

A radio button pst presents a pst of mutually exclusive options. A check box pst presents a pst of independent options. These controls contain a collection of ListItem objects that could be referred to through the Items property of the control.

Basic syntax of radio button pst:

<asp:RadioButtonList ID="RadioButtonList1" runat="server" AutoPostBack="True" 
   OnSelectedIndexChanged="RadioButtonList1_SelectedIndexChanged">
</asp:RadioButtonList>

Basic syntax of check box pst:

<asp:CheckBoxList ID="CheckBoxList1" runat="server" AutoPostBack="True" 
   OnSelectedIndexChanged="CheckBoxList1_SelectedIndexChanged">
</asp:CheckBoxList>

Common properties of check box and radio button psts:

Bulleted psts and Numbered psts

The bulleted pst control creates bulleted psts or numbered psts. These controls contain a collection of ListItem objects that could be referred to through the Items property of the control.

Basic syntax of a bulleted pst:

<asp:BulletedList ID="BulletedList1" runat="server">
</asp:BulletedList>

Common properties of the bulleted pst:

HyperLink Control

The HyperLink control is pke the HTML <a> element.

Basic syntax for a hyperpnk control:

<asp:HyperLink ID="HyperLink1" runat="server">
   HyperLink
</asp:HyperLink>

It has the following important properties:

Image Control

The image control is used for displaying images on the web page, or some alternative text, if the image is not available.

Basic syntax for an image control:

<asp:Image ID="Image1" runat="server">

It has the following important properties: