program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace NumChoose
{
    static class Program
    {
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
            //DecimalPlaces 数字显示框中要显示的十进制数
            //Hexadeccimal 指示数字是否以十六进制格式显示所包括的的值
            //Increment 向上或向下单击button时,数字显示框递增或递减的值
            //InterceptArrowKeys 指示用户能否够使用向上或向下键选择值
            //Maximum 显示框最大值
            //Minumum 显示框最小同意值
            //Value NumericUpDown 空间中显示的数值
            //UpDownAlign 显示框中向上或向下button的对齐方式
            //DownButton 减小数字显示框中的值
            //UpButton 添加数字显示框中的值
        }
    }
}

Form1.cs:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace NumChoose
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            numericUpDown1.Minimum = 1;  //设置最小值1
            numericUpDown1.Maximum = 20;  //设置最大值20
            numericUpDown1.DecimalPlaces = 2; //设置空间的DecimaPlaces属性,使空间的数值小数点后两位显示
            numericUpDown1.Increment = 1; //设置递增或递减
            numericUpDown1.InterceptArrowKeys = true;//设置用户能够通过向上,向下键选择值

        }

        private void numericUpDown1_ValueChanged(object sender, EventArgs e)
        {
            label2.Text = "选中的数值为: " + numericUpDown1.Value;
        }
    }
}

Form1设计:

namespace NumChoose
{
    partial class Form1
    {
        /// <summary>
        /// 必需的设计器变量。
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// 清理全部正在使用的资源。
        /// </summary>
        /// <param name="disposing">假设应释放托管资源，为 true；否则为 false。</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows 窗口设计器生成的代码

        /// <summary>
        /// 设计器支持所需的方法 - 不要
        /// 使用代码编辑器改动此方法的内容。
        /// </summary>
        private void InitializeComponent()
        {
            this.numericUpDown1 = new System.Windows.Forms.NumericUpDown();
            this.label1 = new System.Windows.Forms.Label();
            this.label2 = new System.Windows.Forms.Label();
            ((System.ComponentModel.ISupportInitialize)(this.numericUpDown1)).BeginInit();
            this.SuspendLayout();
            // 
            // numericUpDown1
            // 
            this.numericUpDown1.Location = new System.Drawing.Point(102, 22);
            this.numericUpDown1.Name = "numericUpDown1";
            this.numericUpDown1.Size = new System.Drawing.Size(120, 21);
            this.numericUpDown1.TabIndex = 0;
            this.numericUpDown1.ValueChanged += new System.EventHandler(this.numericUpDown1_ValueChanged);
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Location = new System.Drawing.Point(37, 26);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(59, 12);
            this.label1.TabIndex = 1;
            this.label1.Text = "选择数字:";
            // 
            // label2
            // 
            this.label2.AutoSize = true;
            this.label2.Location = new System.Drawing.Point(37, 62);
            this.label2.Name = "label2";
            this.label2.Size = new System.Drawing.Size(0, 12);
            this.label2.TabIndex = 2;
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(305, 121);
            this.Controls.Add(this.label2);
            this.Controls.Add(this.label1);
            this.Controls.Add(this.numericUpDown1);
            this.Name = "Form1";
            this.Text = "数字选择";
            this.Load += new System.EventHandler(this.Form1_Load);
            ((System.ComponentModel.ISupportInitialize)(this.numericUpDown1)).EndInit();
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.NumericUpDown numericUpDown1;
        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.Label label2;
    }
}