C#的checked关键字判断是否溢出

一、定义

二、示例：

三、生成：

一、定义

使用checked关键字处理溢出。

在进行数学运算时，由于变量类型不同，数值的值域也有所不同。如果变量中的数值超出了变量的值域，则会出现溢出情况，出现溢出时变量中的数值将不准确。怎样有效地防止溢出呢?下面结合实例演示怎样使用checked关键字检查是否出现溢出。

例如，数值类型为byte，byte类型的值域为0～255，所以如果byte类型变量的值高于255或者小于0都会出现溢出。

二、示例：

// 使用checked关键字判断是否有溢出
namespace _022
{public partial class Form1 : Form{private Label? label1;private Label? label2;private Button? button1;private TextBox? textBox1;private TextBox? textBox2;private TextBox? textBox3;public Form1(){InitializeComponent();Load += Form1_Load;}private void Form1_Load(object? sender, EventArgs e){// // label1// label1 = new Label{AutoSize = true,Location = new Point(65, 18),Name = "label1",Size = new Size(43, 17),TabIndex = 0,Text = " + "};// // label2// label2 = new Label{AutoSize = true,Location = new Point(150, 18),Name = "label2",Size = new Size(43, 17),TabIndex = 7,Text = " = "};// // button1// button1 = new Button{Location = new Point(247, 15),Name = "button1",Size = new Size(75, 23),TabIndex = 3,Text = "计算",UseVisualStyleBackColor = true};button1.Click += Button1_Click;// // textBox1// textBox1 = new TextBox{Location = new Point(12, 15),Name = "textBox1",Size = new Size(50, 23),TabIndex = 4,Text = "100"};// // textBox2// textBox2 = new TextBox{Location = new Point(99, 15),Name = "textBox2",Size = new Size(50, 23),TabIndex = 5,Text = "200"};// // textBox3// textBox3 = new TextBox{Location = new Point(182, 15),Name = "textBox3",Size = new Size(50, 23),TabIndex = 6};// // Form1// AutoScaleDimensions = new SizeF(7F, 17F);AutoScaleMode = AutoScaleMode.Font;ClientSize = new Size(334, 91);Controls.Add(label2);Controls.Add(textBox3);Controls.Add(textBox2);Controls.Add(textBox1);Controls.Add(button1);Controls.Add(label1);Name = "Form1";StartPosition = FormStartPosition.CenterScreen;Text = "使用checked关键字处理溢出";           }private void Button1_Click(object? sender, EventArgs e){if (byte.TryParse(                             //对两个byte类型变量赋值textBox1!.Text, out byte Add_One)&& byte.TryParse(textBox2!.Text, out byte Add_Two)){try{checked { Add_One += Add_Two; }        //使用checke关键字判断是否有溢出textBox3!.Text = Add_One.ToString();   //输出相加后的结果}catch (OverflowException ex){MessageBox.Show(ex.Message, "出错！"); //输出异常信息}}else{MessageBox.Show("请输入255以内的数字!");    //输出错误信息}}}
}