Kevin,
You asked how to convert char (unicode) to byte. But substring returns a string.
System.Text.Encoding.ASCII.GetBytes(sString) would return a byte[].
As I see you need it to validate a time string. Then you might instead directly use DateTime class' Parse.
Cetin

>Not sure why this doesn't work. ascVal contains the character
>from the substring.
>
>Here's my code:
>
>

>for(int iChar = 1; iChar < sTime.Length; iChar++)
>{
>  sChar = sTime.Substring(iChar - 1, 1);
>
>  byte ascVal = System.Convert.ToByte(sChar);
>
>  // Allowable values are 0-9,';','A','M','P'
>  if ((iValue >= 48 && iValue <= 57) ||
>    iValue == 58 ||
>    iValue == 59 ||
>    iValue == 77 ||
>    iValue == 80)
>  {
>  }
>  else
>    bValid = false;
>
>}
>
>

>
>
>
>
>>>I am extracting characters from a string.
>>>
>>>How can I determine the ASCII value of the characters?
>>>
>>>Thanks
>>
>>byte ascVal = System.Convert.ToByte(char);
>>
>>Cetin