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

namespace UAS_MES_NEW.CustomControl.TextBoxWithIcon
{
    public partial class TextBoxNumOnly : TextBox
    {
        public TextBoxNumOnly()
        {
            InitializeComponent();
            this.KeyPress += OnKeyPress;
            this.Enter += OnEnter;
            this.Leave += OnLeave;
        }

        /// <summary>
        /// 防止返回的内容为空
        /// </summary>
        public override string Text
        {
            get
            {
                //如果未输入值则自动的返回0，防止值类型转换的时候进行异常处理
                if (base.Text == "")
                {
                    return "0";
                }
                return base.Text;
            }

            set
            {
                base.Text = value;
            }
        }

        private void OnKeyPress(object sender, KeyPressEventArgs e)
        {
            if (e.KeyChar != '\b')//这是允许输入退格键
            {
                if ((e.KeyChar < '0') || (e.KeyChar > '9'))//这是允许输入0-9数字
                {
                    e.Handled = true;
                }
            }
        }

        private void OnEnter(object sender, EventArgs e)
        {
            BackColor = Color.GreenYellow;
        }

        private void OnLeave(object sender, EventArgs e)
        {
            BackColor = Color.White;
        }
    }
}