private void calculate()
{
String expr = textBox1.Text;
textBox1.Clear();
textBox1.Text = SevenConverter.FromDec(Expression.ParseExpr(ref expr));
}
public static int ParseNumber(ref string expr)
{
string numberTemp = "";
int initialLength = expr.Length;
for (int i = 0; i < initialLength; i++)
{
if (char.IsDigit(expr[0]))
{
numberTemp += expr[0];
expr = expr.Substring(1, expr.Length - 1);
}
else
{
break;
}
}
return(SevenConverter.ToDec(numberTemp));
}