byte转string字符

foreach(DataRow row in ds.Tables[0].Rows)
{
    byte[] datbytes = (byte[])row["dat"];
    for(int i = 0; i < datbytes.Length; i++)
       {                                    
         smartdat[i] = (char)datbytes[i];
       }
     String dat = new String(smartdat);                                
     dat = System.Text.RegularExpressions.Regex.Replace(dat, @"[^0-9,]+", "");//只保留数字
}