private string GetExpression(List <OperationBase> checkedOperations, int numbers)
{
string exp = string.Empty;
int[] arr = new int[numbers];
for (int i = 0; i < numbers; i++)
{
OperationBase operation = GetOperation(checkedOperations, checkedOperations.Count);
if (i == 0)
{
arr[i] = operation.GenerateFirstNumber();
exp += arr[i];
continue;
}
int start = arr[i - 1];
int value = operation.GenerateNextNumber(start);
exp += (operation.Operator + value);
arr[i] = Convert.ToInt32(new DataTable().Compute(exp.Replace('x', '*'), null));
if (i == numbers - 1)
{
exp += "=";
}
}
return(exp);
}