>Hi,
>I have item as below:
>
>

>ItemName          BeforeItem    AfterItem
>------------------------------------------
>"First"
>"Second"
>"Third"
>"B4Second"        "Second"
>"BetweenSecond"   "Second"      "B4Second"
>
>

>
>I would like to implement IComparable to sort them so that it could be as below:
>
>First
>B4Second
>BetweenSecond
>Second
>Third
>
>Please advice
>
>Thank you
___________
There is nothing in your definition that states that
- First has to come before Second
- Second has to come before Third


Anyway, in order to accomplish such things you can do a topological sort, which will give you likely the following output
since there is no dependency between any of First, Second and Third

Third
First
B4Second
BetweenSecond
Second

If we suppose that rows with empty BeforeItem and empty AfterItem imply a natural order, then I can produce your output


sample program

		static void doit()
		{
			string [,] s  = 
				// 
			{	{ "First", null, null}, 
				{ "Second", null, null }, 
				{ "Third", null, null }, 
				{ "B4Second", "Second", null },
				{ "BetweenSecond", "Second", "B4Second" }
			} ;

			SortThem(s, true);
		}

		static void SortThem( string[,] s, bool respectInputOrder) 
		{

			var v = new Graph.TopologicalSort<string>();
			int i;
			string successor, predecessor, lastItem = null;


			for (i = 0; i < s.GetLength(0); i++)
			{

				// 0 and 1
				predecessor = s[i, 0];
				successor = s[i, 1];

				if (respectInputOrder && (successor == null) && (s[i, 2] == null) )
				{
					if (lastItem != null && !v.Edge(predecessor, lastItem))
							throw new Exception("program error");

					lastItem = predecessor ;
				}

				if (successor == null)
				{
					if (!v.Edge(predecessor))
						throw new Exception("program error");
				}
				else
				{	
					if( !v.Edge(successor, predecessor) )
						throw new Exception("program error");
				}
				
				// 1 && 2
				
				successor = predecessor ; // s[i, 0]
				predecessor = s[i, 2];

				if (predecessor != null)
				{
					if (!v.Edge(successor, predecessor))
						throw new Exception("program error");
				}
	
			}

			// Sort them
			Queue<string> output;

			if (!v.Sort(out output))
			{	// cycles
				Console.WriteLine("a cycle has been detected");
				while (output.Count > 0)
					Console.WriteLine(output.Dequeue());

			}
			else
			{
				Console.WriteLine("Evaluation order is");
				while (output.Count > 0)
					Console.WriteLine(output.Dequeue());
			}
		}

Topological sort can be downloaded here: http://www.atoutfox.com/articles.asp?ACTION=FCONSULTER&ID=0000000526

UPDATE
Changed download to work with IEquatable instead of IComparable