控件属性和InitializeComponent()关系：

 1 namespace Test22
 2 {
 3     partial class Form1
 4     {
 5         /// <summary>
 6         /// 必需的设计器变量。
 7         /// </summary>
 8         private System.ComponentModel.IContainer components = null;
 9 
10         /// <summary>
11         /// 清理所有正在使用的资源。
12         /// </summary>
13         /// <param name="disposing">如果应释放托管资源，为 true；否则为 false。</param>
14         protected override void Dispose(bool disposing)
15         {
16             if (disposing && (components != null))
17             {
18                 components.Dispose();
19             }
20             base.Dispose(disposing);
21         }
22 
23         #region Windows 窗体设计器生成的代码
24 
25         /// <summary>
26         /// 设计器支持所需的方法 - 不要
27         /// 使用代码编辑器修改此方法的内容。
28         /// </summary>
29         private void InitializeComponent()
30         {
31             this.numericUpDown1 = new System.Windows.Forms.NumericUpDown();
32             ((System.ComponentModel.ISupportInitialize)(this.numericUpDown1)).BeginInit();
33             this.SuspendLayout();
34             // 
35             // numericUpDown1
36             // 
37             this.numericUpDown1.DecimalPlaces = 4;//属性里对应！！！！！
38             this.numericUpDown1.Location = new System.Drawing.Point(12, 12);
39             this.numericUpDown1.Name = "numericUpDown1";
40             this.numericUpDown1.Size = new System.Drawing.Size(120, 21);
41             this.numericUpDown1.TabIndex = 0;
42             // 
43             // Form1
44             // 
45             this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
46             this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
47             this.ClientSize = new System.Drawing.Size(153, 53);
48             this.Controls.Add(this.numericUpDown1);
49             this.Name = "Form1";
50             this.Text = "Form1";
51             this.Load += new System.EventHandler(this.Form1_Load);
52             ((System.ComponentModel.ISupportInitialize)(this.numericUpDown1)).EndInit();
53             this.ResumeLayout(false);
54 
55         }
56 
57         #endregion
58 
59         private System.Windows.Forms.NumericUpDown numericUpDown1;
60     }
61 }

控件中小数点位数和InitializeComponent()里面的代码相呼应，而下面的代码又设置了2，所以覆盖掉了，代码和运行结果如下：

 1 using System;
 2 using System.Data;
 3 using System.Drawing;
 4 using System.Text;
 5 using System.Windows.Forms;
 6 namespace Test22
 7 {
 8     public partial class Form1 : Form
 9     {
10         public Form1()
11         {
12             InitializeComponent();
13         }
14         private void Form1_Load(object sender, EventArgs e)
15         {
16             numericUpDown1.Maximum = 20;
17             numericUpDown1.Minimum = 1;
18             numericUpDown1.DecimalPlaces = 2;
19         }
20     }
21 }