C# 中的複選框

CheckBox 是一個允許使用者從選項清單中進行單一或多個選擇的控制項。在 C# 中，System.Windows.Forms 命名空間中的 CheckBox 類別用於處理複選框控制項。它是 Windows 窗體的一部分，用於取得使用者的輸入。它也可用於從 true/false 或 yes/no 等選項中進行選擇。

使用者可以點擊複選框來選擇關聯的項目，並可以再次按一下它來取消選擇該項目。它可以與圖像或文字或兩者一起使用。

複選框的類型

我們可以用兩種不同的方式來建立複選框：

1. 設計時使用表單設計器。
2. 在執行時在程式碼中使用 CheckBox 類別。

我們可以在設計時建立複選框，方法是從工具箱中拖曳複選框控件，然後將其放在 Windows 窗體上。然後，我們可以進入複選框控制項的屬性並對其進行修改。

要在執行時建立複選框，我們需要使用 CheckBox 類別。

文法：

CheckBox check_box = new CheckBox();

之後，我們就可以依照自己的需求設定複選框的屬性了。

//setting location of checkbox
check_box.Location = new Point(300,150);
//setting height and width for checkbox
check_box.Height = 50;
check_box.Width = 50;
//setting text for checkbox
check_box.Text = “Yes”;

最後，我們需要使用以下方法將此複選框新增至 Windows 窗體：

this.Controls.Add(check_box);

複選框屬性

C# 為複選框提供了許多屬性。

Property	Description
AllowDrop	It is used to get or set a value that determines whether the checkbox control can accept data that a user drags onto it.
Appearance	It is used to get or set a value that determines the appearance of the checkbox control.
AutoCheck	It is used to get or set a value that determines whether the values of the Checked or CheckState properties or the appearance of the checkbox are automatically changed when the checkbox is clicked.
AutoSize	It is used to get or set a value that determines whether the checkbox control resizes based on its content.
BackColor	It is used to get or set the background color of the checkbox control.
BackGroundImage	It is used to get or set the background image displayed in the checkbox control.
CanFocus	It is used to get a value that determines whether the checkbox control can receive focus.
Checked	It is used to get or set a value that determines whether the checkbox control is in the checked state.
CheckState	It is used to get or set the state of the checkbox.
DefaultSize	It is used to get the default size of the checkbox control.
Enabled	It is used to get or set a value that determines whether the checkbox control can respond to user interaction.
Focused	It is used to get a value that determines whether the checkbox control has input focus.
Font	It is used to get or set the font of text displayed by the checkbox control.
ForeColor	It is used to get or set the foreground color of the checkbox control.
Height	It is used to get or set the height of the checkbox control.
Image	It is used to get or set the image which is displayed on the checkbox control.
Location	It is used to get or set the coordinates of the upper left corner of the control relative to the upper left corner of its parent container.
Margin	It is used to get or set the space between controls.
Name	It is used to get or set the name of the checkbox control.
Size	It is used to get or set the height and width of the checkbox control.
Text	It is used to get or set the text associated with the checkbox control.
ThreeState	It is used to get or set a value that determines whether the checkbox will allow three check states instead of two.
Width	It is used to get or set the width of the checkbox control.

CheckBox Events

Let us see some important events for the CheckBox provided by C#:

Event	Description
CheckedChanged	This event occurs when the value of Checked property changes.
CheckStateChanged	This event occurs when the value of CheckState property changes.
Click	This event occurs when the checkbox is clicked.
GotFocus	This event occurs when the checkbox receives focus.
Leave	This event occurs when the input focus leaves the checkbox.
LostFocus	This event occurs when the checkbox loses focus.
MouseClick	This event occurs when the checkbox is clicked by the mouse.
MouseDoubleClick	This event occurs when the checkbox is double-clicked by a mouse.
TextChanged	This event occurs when the value of Text property changes.

Implementation of CheckBox in C#

Below is an example of how to implement the checkbox in c #

Example:

Code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace WindowsFormsApp1
{
public partial class CheckBoxDemo : Form
{
public CheckBoxDemo()
{
InitializeComponent();
}
private void CheckBoxDemo_Load(object sender, EventArgs e)
{
//Creating and setting properties of Label
Label label = new Label();
label.Text = "Select your technical skills";
label.AutoSize = true;
label.Location = new Point(192, 77);
label.Font = new Font("Microsoft Sans Serif", 11);
//Adding label to form
this.Controls.Add(label);
//Creating and setting properties of CheckBox
CheckBox checkbox1 = new CheckBox();
checkbox1.Location = new Point(195, 111);
checkbox1.Text = "C";
//Adding checkbox to form
this.Controls.Add(checkbox1);
CheckBox checkbox2 = new CheckBox();
checkbox2.Location = new Point(195, 156);
checkbox2.Text = "C++";
this.Controls.Add(checkbox2);
CheckBox checkbox3 = new CheckBox();
checkbox3.Location = new Point(195, 195);
checkbox3.Text = "C#";
this.Controls.Add(checkbox3);
CheckBox checkbox4 = new CheckBox();
checkbox4.Location = new Point(195, 235);
checkbox4.Text = "JAVA";
this.Controls.Add(checkbox4);
CheckBox checkbox5 = new CheckBox();
checkbox5.Location = new Point(195, 275);
checkbox5.Text = "HTML";
this.Controls.Add(checkbox5);
}
}
}

Output:

Conclusion – Checkbox in C#

A checkbox in C# can also have an indeterminate state. This can be achieved by setting the CheckState property to ‘Indeterminate. It is a state between ‘Yes’ and ‘No’ in which the checkbox will neither be checked nor unchecked.

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