C# 判断一个字符串是否数字开头

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;
  using System.Text.RegularExpressions;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
     
         
        private void button1_Click(object sender, EventArgs e)
        {
            Regex regChina = new Regex("^[^\x00-\xFF]");
            Regex regNum = new Regex("^[0-9]");
            Regex regChar = new Regex("^[a-z]");
            Regex regDChar = new Regex("^[A-Z]");
            string str = "YL闫磊";
            if (regNum.IsMatch(str))
            {
                MessageBox.Show("是数字");
            }
            else if (regChina.IsMatch(str))
            {
                MessageBox.Show("是中文");
            }
            else if (regChar.IsMatch(str))
            {
                MessageBox.Show("小写");
            }
            else if (regDChar.IsMatch(str))
            {
                MessageBox.Show("大写");
            }
        }
    }
}