1using System;
 2
 3namespace override_attribute_event
 4{
 5    
 6    public class NumericTextBox : System.Windows.Forms.TextBox
 7    {
 8        public NumericTextBox()
 9        {
10            //
11            // TODO: 在此处添加构造函数逻辑
12            //
13        }
14
15        //重载TextBox的Text属性
16        public override string Text
17        {
18            get
19            {
20                return base.Text;
21            }
22            set
23            {
24                try
25                {
26                    int.Parse(value);
27                    base.Text = value;
28                    return;
29                }
30                catch
31                {
32                    //如果输入文本部为数值，则不作任何操作
33                }
34                //输入文本为空的时候也可行
35                if (value == null)
36                {
37                    base.Text = value;
38                    return;
39                }
40            }
41        }
42
43        //重载了TextBox的OnKeyPress事件，不让用户点击数字键和Backspace键以外的键
44        protected override void OnKeyPress(System.Windows.Forms.KeyPressEventArgs e)
45        {
46            //判断用户的按键
47            int asciiInteger = Convert.ToInt32(e.KeyChar);
48            if (asciiInteger >= 47 && asciiInteger <= 57)
49            {
50                e.Handled = false;//将TextBox自身的OnKeyPress触发，实现了数字键的文本输入
51                return;
52            }
53            if (asciiInteger == 8)
54            {
55                e.Handled = false;
56                return;
57            }
58            e.Handled = true;
59            //如果用户点击了非数字键，则调用自定义的事件InvalidUserEntry
60            if (InvalidUserEntry != null)
61            {
62                InvalidUserEntry(this,e);
63            }
64        }
65
66        //自定义事件
67        public delegate void MyEvent(object sender,System.Windows.Forms.KeyPressEventArgs e);
68
69        public event MyEvent InvalidUserEntry;
70
71
72        
73    }
74}
75

完整源代码下载：override_attribute_event.rar