FROM : https://www.cnblogs.com/ilookbo/p/4828722.html
/// <summary>
/// 判断输入的字符串是否只包含数字和英文字母
/// </summary>
/// <param name="input"></param>
/// <returns></returns>
public static bool IsNumAndEnCh(string input)
{
string pattern = @"^[A-Za-z0-9]+$";
Regex regex = new Regex(pattern);
return regex.IsMatch(input);
}