## ASP.NET HtmlInputCheckBox Control
The `HtmlInputCheckBox` control is an HTML server control in ASP.NET used to programmatically control and interact with the HTML `` element on the server side. It allows developers to create, manipulate, and read the state of checkboxes within web forms.
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## Definition and Usage
In standard HTML, the `` element is used to let users select one or more options from a set. By adding the `runat="server"` attribute to this element, ASP.NET converts it into an `HtmlInputCheckBox` control. This enables server-side code to detect whether the checkbox is checked, modify its state dynamically, and respond to user interactions during postbacks.
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## Properties and Events
### Properties
The following table lists the key properties of the `HtmlInputCheckBox` control:
| Property | Type | Description |
| :--- | :--- | :--- |
| `Attributes` | `AttributeCollection` | Returns a collection of all attribute name-and-value pairs declared on the element. |
| `Checked` | `Boolean` | Gets or sets a value indicating whether the checkbox is currently selected (checked). `true` if checked; otherwise, `false`. |
| `Disabled` | `Boolean` | Gets or sets a value indicating whether the control is disabled. The default is `false`. |
| `ID` | `String` | The unique identifier assigned to the control. |
| `Name` | `String` | The unique group name for the HTML element. |
| `Runat` | `String` | Specifies that the control is a server control. Must be set to `"server"`. |
| `Style` | `CssStyleCollection` | Gets a collection of all CSS styles applied to the control. |
| `TagName` | `String` | Returns the tag name of the element (always `"input"`). |
| `Type` | `String` | Returns the type of the input element (always `"checkbox"`). |
| `Value` | `String` | Gets or sets the value associated with the checkbox element. |
| `Visible` | `Boolean` | Gets or sets a value indicating whether the control is rendered on the page. |
### Events
| Event | Description |
| :--- | :--- |
| `ServerChange` | Occurs when the state of the checkbox (checked/unchecked) changes between posts to the server. |
---
## Code Example
The following example demonstrates how to use the `HtmlInputCheckBox` control in an `.aspx` page.
In this example, we declare two `HtmlInputCheckBox` controls, an `HtmlInputButton` control, and an `HtmlGenericControl` (a `
` element) to display the output. When the submit button is clicked, the server-side `SubmitBtn_Click` method runs, checks the state of each checkbox, and updates the paragraph text accordingly.
### ASPX Page (`Default.aspx`)
```html
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
HtmlInputCheckBox Example
```
### Code-Behind (`Default.aspx.cs`)
```csharp
using System;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
// Initialization logic (if any)
}
protected void SubmitBtn_Click(object sender, EventArgs e)
{
pMessage.InnerHtml = "";
// Check if the "Red" checkbox is selected
if (chkRed.Checked)
{
pMessage.InnerHtml += "You prefer red! ";
}
// Check if the "Blue" checkbox is selected
if (chkBlue.Checked)
{
pMessage.InnerHtml += "You prefer blue! ";
}
// If neither is selected
if (!chkRed.Checked && !chkBlue.Checked)
{
pMessage.InnerHtml = "You did not select any color.";
}
}
}
```
---
## Considerations
1. **Form Requirement**: Like all HTML server controls, the `HtmlInputCheckBox` must be nested inside a `
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