C# : How to get running combination from two List<String> based on a master list

Dear all , this is something like my previous question How to get moving combination from two List<String> in C#?

I'm having a masterlist and two childlist like below

        List<String> MasterList = new List<string&开发者_StackOverflowgt; { "A", "B", "C", "D", "E" };
        List<String> ListOne = new List<string> { "A", "B", "C" };
        List<String> ListTwo = new List<String> { "B", "D" };

I just need to get the running combination from the above list for that i'm using like(previous question's answer(Thanks Danny Chen))

        List<String> Result = new List<string>();
        Result = ListOne.SelectMany((a, indexA) => ListTwo
                                    .Where((b, indexB) => ListTwo
                                    .Contains(a) ? !b.Equals(a) && indexB > indexA : 
                                    !b.Equals(a)).Select(b => string.Format("{0}-{1}", a, b))).ToList(); 

so the Result list will contain

        "A-B"
        "A-D"
        "B-D"
        "C-B"
        "C-D"

Now my problem is the sorting issue

In the above result the fourth entry is C-B but it should be B-C. Because in the MasterList the C is after B.

How to do this in my existing linq .

Please help me to do this.

---

Not really clear on the exact requirement here, so does the MasterList dictate which of the two items should appear first? What about the order of the X1-X2 list? i.e. should B-C appear before B-D because C appears before D in the MasterList?

Anyway, here's something that produces the result you've asked for so far:

List<String> MasterList = new List<string> { "A", "B", "C", "D", "E" };
List<String> ListOne = new List<string> { "A", "B", "C" };
List<String> ListTwo = new List<String> { "B", "D" };

ListOne.SelectMany(i => 
ListTwo.Where(i2 => i != i2)
       .Select(i2 => 
            {
                if (MasterList.IndexOf(i) < MasterList.IndexOf(i2))
                    return string.Format("{0}-{1}", i, i2);
                else
                    return string.Format("{0}-{1}", i2, i);
            }
       ));

outputs:

A-B
A-D
B-D
B-C
C-D