//Visual Basic 2008/2010 Recursie Procedures en Functies
public class Exercise4Solution {
    void Main() {
        int[] numbers;
        int number;
        int lowerbound;
        int upperbound;
        bool found;
        number = 15;
        lowerbound = 0;
        upperbound = 9;
        found = this.BinarySearch(number, numbers, lowerbound, upperbound);
        Console.WriteLine(found);
        number = 18;
        lowerbound = 0;
        upperbound = 7;
        found = this.BinarySearch(number, numbers, lowerbound, upperbound);
        Console.WriteLine(found);
        Console.ReadLine();
    }
    void BinarySearch(int number, int[] array, int lowerbound, int upperbound) {
        int middle = ((lowerbound + upperbound) 
                    / 2);
        if ((number == this.array(middle))) {
            BinarySearch = true;
        }
        else {
            if ((upperbound <= lowerbound)) {
                BinarySearch = false;
            }
            else {
                if ((number > this.array(middle))) {
                    lowerbound = (middle + 1);
                }
                else {
                    upperbound = (middle - 1);
                }
                BinarySearch = this.BinarySearch(number, array, lowerbound, upperbound);
            }
        }
    }
}
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