Using LINQ to join two string lists without repeats

I have a list of members that have to play a game against each other and I want to generate a complete list of all the members against every other member without repeating any games. My list looks like this:

string[] members = {"Alphie", "Jerome", "Silky", "Buzz" };

My first attempt at generating a list using LINQ was this:

IEnumerable<string> q = from one in members
                        from two in members
                        select one + " plays " + two;

which resulted in:

Alphie plays Alphie
Alphie plays Jerome
Alphie plays Silky
Alphie plays Buzz
Jerome plays Alphie
Jerome plays Jerome
Jerome plays Silky
Jerome plays Buzz
Silky plays Alphie
Silky plays Jerome
Silky plays Silky
Silky plays Buzz
Buzz plays Alphie
Buzz plays Jerome
Buzz plays Silky
Buzz plays Buzz

This is not exactly what I was looking for. I wonder who the winner would have been in Buzz versus Buzz?

The secret is to put a where clause before the select statement:

where one.CompareTo(two) < 0

This will eliminate duplicates when CompareTo(two) == 0 and also alphabetically sort the two players eliminating them playing against each other a second time. This is the complete code snippet:

IEnumerable<string> q = from one in members
                        from two in members
                        where one.CompareTo(two) < 0
                        select one + " plays " + two;

and here are the revised results:

Alphie plays Jerome
Alphie plays Silky
Alphie plays Buzz
Jerome plays Silky
Buzz plays Jerome
Buzz plays Silky
 
 

LINQ to XML Notes

Some notes on LINQ to XML

• All LINQ to XML objects inherit from XObject.
• All LINQ to XML objects except XAttribute inherit from XNode which directly inherits from XObject.
• Using XDocument is optional. (XDocument wraps an XElement object and adds to it.)
• Both XDocument and XElement have static methods Load and Parse to load XML.
• Load() can build an X-DOM from a TextReader, XmlReader, a file or a URI (such as a web service or RSS feed).
• Parse can build an X-DOM from a fragment of XML in a string.

Hashtable keys intersect with list of Int32

The problem: You have a classic Hashtable. Although the keys are strings they hold only ints. You also have a list of ints. You want to find out if any of the keys from the Hashtable are in the list of ints. How do you do this in one line of LINQ?

The solution, using LINQ, that I came up with is:

            // Setup the test data
            System.Collections.Hashtable ht = new System.Collections.Hashtable();
            ht.Add("1", new object());
            ht.Add("2", new object());

            List<int> second = new List<int>();
            second.Add(2);
            second.Add(3);

            // Query the data
            bool containsKey = ht.Keys.Cast<string>().Select(a => Convert.ToInt32(a)).ToList().Intersect(second).Count() > 0;

            // Print the result
            Console.Write("Contains Key: {0}", containsKey);