Task: Sum to 100
Java: 
package rosettacode;

import java.io.PrintStream;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class SumTo100 implements Runnable {

    public static void main(String[] args) {
        new SumTo100().run();
    }

    void print(int givenSum) {
        Expression expression = new Expression();
        for (int i = 0; i < Expression.NUMBER_OF_EXPRESSIONS; i++, expression.next()) {
            if (expression.toInt() == givenSum) {
                expression.print();
            }
        }
    }

    void comment(String commentString) {
        System.out.println();
        System.out.println(commentString);
        System.out.println();
    }

    @Override
    public void run() {
        final Stat stat = new Stat();

        comment("Show all solutions that sum to 100");
        final int givenSum = 100;
        print(givenSum);

        comment("Show the sum that has the maximum number of solutions");
        final int maxCount = Collections.max(stat.sumCount.keySet());
        int maxSum;
        Iterator<Integer> it = stat.sumCount.get(maxCount).iterator();
        do {
            maxSum = it.next();
        } while (maxSum < 0);
        System.out.println(maxSum + " has " + maxCount + " solutions");

        comment("Show the lowest positive number that can't be expressed");
        int value = 0;
        while (stat.countSum.containsKey(value)) {
            value++;
        }
        System.out.println(value);

        comment("Show the ten highest numbers that can be expressed");
        final int n = stat.countSum.keySet().size();
        final Integer[] sums = stat.countSum.keySet().toArray(new Integer[n]);
        Arrays.sort(sums);
        for (int i = n - 1; i >= n - 10; i--) {
            print(sums[i]);
        }
    }

    private static class Expression {

        private final static int NUMBER_OF_DIGITS = 9;
        private final static byte ADD = 0;
        private final static byte SUB = 1;
        private final static byte JOIN = 2;

        final byte[] code = new byte[NUMBER_OF_DIGITS];
        final static int NUMBER_OF_EXPRESSIONS = 2 * 3 * 3 * 3 * 3 * 3 * 3 * 3 * 3;

        Expression next() {
            for (int i = 0; i < NUMBER_OF_DIGITS; i++) {
                if (++code[i] > JOIN) {
                    code[i] = ADD;
                } else {
                    break;
                }
            }
            return this;
        }

        int toInt() {
            int value = 0;
            int number = 0;
            int sign = (+1);
            for (int digit = 1; digit <= 9; digit++) {
                switch (code[NUMBER_OF_DIGITS - digit]) {
                    case ADD:
                        value += sign * number;
                        number = digit;
                        sign = (+1);
                        break;
                    case SUB:
                        value += sign * number;
                        number = digit;
                        sign = (-1);
                        break;
                    case JOIN:
                        number = 10 * number + digit;
                        break;
                }
            }
            return value + sign * number;
        }

        @Override
        public String toString() {
            StringBuilder s = new StringBuilder(2 * NUMBER_OF_DIGITS + 1);
            for (int digit = 1; digit <= NUMBER_OF_DIGITS; digit++) {
                switch (code[NUMBER_OF_DIGITS - digit]) {
                    case ADD:
                        if (digit > 1) {
                            s.append('+');
                        }
                        break;
                    case SUB:
                        s.append('-');
                        break;
                }
                s.append(digit);
            }
            return s.toString();
        }

        void print() {
            print(System.out);
        }

        void print(PrintStream printStream) {
            printStream.format("%9d", this.toInt());
            printStream.println(" = " + this);
        }
    }

    private static class Stat {

        final Map<Integer, Integer> countSum = new HashMap<>();
        final Map<Integer, Set<Integer>> sumCount = new HashMap<>();

        Stat() {
            Expression expression = new Expression();
            for (int i = 0; i < Expression.NUMBER_OF_EXPRESSIONS; i++, expression.next()) {
                int sum = expression.toInt();
                countSum.put(sum, countSum.getOrDefault(sum, 0) + 1);
            }
            for (Map.Entry<Integer, Integer> entry : countSum.entrySet()) {
                Set<Integer> set;
                if (sumCount.containsKey(entry.getValue())) {
                    set = sumCount.get(entry.getValue());
                } else {
                    set = new HashSet<>();
                }
                set.add(entry.getKey());
                sumCount.put(entry.getValue(), set);
            }
        }
    }
}

VB: 
Function plusOne(iAry() As Integer, spot As Integer) As Integer
    Dim spotLim As Integer = If(spot = 0, 1, 2) 
    If iAry(spot) = spotLim Then 
        If spot = 0 Then Return -1 
        iAry(spot) = 0 
        Return plusOne(iAry, spot - 1) 
    Else
        iAry(spot) += 1 
    End If
    Return spot
End Function


Function generate(iAry() As Integer, terms As String) As String
    Dim operations As String() = {"", "-", "+"} 
    generate = ""
    For i As Integer = 0 To iAry.Count - 1
        generate &= operations(iAry(i)) & Mid(terms, i + 1, 1).ToString()
    Next
End Function


Function eval(sequence As String) As Integer
    eval = 0
    Dim term As Integer = 0, operation As Integer = 1
    For Each ch As Char In sequence
        Select Case ch
            Case "-", "+" 
                eval += If(operation = 0, -term, term) : term = 0 
                operation = If(ch = "-", 0, 1) 
            Case Else 
                term = term * 10 + Val(ch)
        End Select
    Next
    eval += If(operation = 0, -term, term) 
End Function


Sub reSort(ByRef first As List(Of Integer), ByRef second As List(Of Integer))
    Dim lou As New List(Of ULong) 
    For i As Integer = 0 To first.Count - 1
        lou.Add((CULng(first(i)) << 32) + second(i)) 
    Next
    lou.Sort()
    For k As Integer = 0 To first.Count - 1
        first(k) = lou(k) >> 32 
        second(k) = lou(k) And &H7FFFFFFF 
    Next
End Sub



Function firstMiss(loi As List(Of Integer))
    Dim low As Integer = 0, high As Integer = loi.Count - 1, middle = (low + high) \ 2
    Do
        If loi(middle) = middle Then low = middle + 1 Else high = middle - 1
        middle = (low + high) \ 2
    Loop Until high <= low
    Return middle + If(loi(middle) = middle, 1, 0)
End Function



Sub Solve100(Optional terms As String = "123456789",
             Optional targSum As Integer = 100,
             Optional highNums As Integer = 10)
    Dim lastDig As Integer = Len(terms) - 1 
    Dim iAry() As Integer = New Integer(lastDig) {} 
    Dim seq As String 
    Dim sVal As Integer 
    Dim sCnt As Integer = 1 
    Dim res As New List(Of Integer) 
    Dim tally As New List(Of Integer) 
    Console.WriteLine("List of solutions that evaluate to 100:")
    Do 
        seq = generate(iAry, terms) 
        sVal = eval(seq) 
        If sVal >= 0 Then 
            If res.Contains(sVal) Then tally(res.IndexOf(sVal)) += 1 _
                                  Else res.Add(sVal) : tally.Add(1)
            If sVal = targSum Then _
                Console.WriteLine(" {0,2} {1}", sCnt, seq) : sCnt += 1
        End If
    Loop Until plusOne(iAry, lastDig) < 0
    reSort(tally, res) 
    Console.WriteLine("The sum that has the the most solutions is {0}, (at {1}).",
                      res.Last, tally.Last)
    reSort(res, tally) 
    Console.WriteLine("The lowest positive sum that can
                      firstMiss(res))
    Console.WriteLine("The ten highest numbers that can be expressed are:")
    res.Reverse() 
    sCnt = 0 
    For Each item As Integer In res.Take(highNums)
        Console.Write("{0, -11}", item)
        sCnt = (sCnt + 1) Mod 5 : If sCnt = 0 Then Console.WriteLine()
    Next
End Sub

Sub Main()
    Solve100() 
End Sub