Complete Guide to ASP.NET Server-Side Tags

ASP.NET provides various server-side tags that allow developers to build dynamic web applications. Below is a complete list of these tags, their descriptions, and examples.

1. Page Directive (`<%@ %>`)

The `<%@ %>` directive is used at the top of an ASPX page to configure settings.

Example:

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

2. Import Directive (`<%@ Import %>`)

Used to import a namespace into the ASPX page.

Example:

<%@ Import Namespace="System.IO" %>

3. Server-Side Code Block (`<% %>`)

Executes server-side C# or VB.NET code.

Example:

<% int number = 10; string message = "Hello, ASP.NET!"; %>

4. Expression Block (`<%= %>`)

Displays a value or variable in the HTML output.

Example:

<p>Today's Date: <%= DateTime.Now %></p>

5. Comment Block (`<%-- --%>`)

Defines server-side comments that are not sent to the client.

Example:

<%-- This is a server-side comment --%>

6. Label Control (``)

Used to display text dynamically.

Example:

<asp:Label ID="lblMessage" runat="server" Text="Welcome!"></asp:Label>

7. TextBox Control (``)

Allows user input.

Example:

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

8. Button Control (``)

Creates a button that performs server-side actions.

Example:

<asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" />

9. GridView Control (``)

Displays data in a tabular format.

Example:

<asp:GridView ID="gvUsers" runat="server" AutoGenerateColumns="True"></asp:GridView>

10. DropDownList Control (``)

Creates a dropdown menu.

Example:

<asp:DropDownList ID="ddlOptions" runat="server"> <asp:ListItem Text="Option 1" Value="1" /> <asp:ListItem Text="Option 2" Value="2" /> </asp:DropDownList>

11. CheckBox Control (``)

Represents a checkbox input.

Example:

<asp:CheckBox ID="chkAgree" runat="server" Text="I agree to the terms" />

12. RequiredFieldValidator (``)

Validates that a field is not empty.

Example:

<asp:RequiredFieldValidator ControlToValidate="txtName" runat="server" ErrorMessage="Name is required" />

13. Session State (`Session[]`)

Stores user data between requests.

Example:

<% Session["UserName"] = "John"; %>

14. Application State (`Application[]`)

Stores application-wide data.

Example:

<% Application["SiteVisitors"] = 100; %>

15. Global.asax (`<script runat=\"server\">`)

Handles application-wide events like `Session_Start` and `Application_BeginRequest`.

Example:

<script runat="server"> void Application_Start(object sender, EventArgs e) { Application["SiteVisitors"] = 0; } </script>

Conclusion

This guide covered the most important **ASP.NET server-side tags**, their purpose, and how they are used in real-world applications.