//不够4位补零
public static string addZero(int val)
{
string str = val + "";
int strLen = str.Length;
if (strLen < 4)
{
while (strLen < 4)
{
StringBuilder sb = new StringBuilder();
sb.Append("0").Append(str);//左补0
//sb.append(str).append("0");//右补0
str = sb.ToString();
strLen = str.Length;
}
}
return str;
}