code for convert string to ascii values

Try This:
int i = 0;
string strInput ="";
string strTemp ="";
//Hold the string value in strInput
strInput = textbox1.text
for (i = 0; i <= strInput.Length - 1; i++)
{
  int charValue = Convert.ToInt32(strInput[i]); // converting in ascii
    if( strTemp =="")
    {
       strTemp = Convert.ToString(charValue);
    }
    else
    {
         strTemp = strTemp + Convert.ToString(charValue);
    }
           
}
Now strTemp will give u the ascii code.
textbox1.text = strTemp ;