How can i do to don't have the same name in my Listbox

Hey Guy,

please i have 3 request.

1 .I don't really know how i can do in C# to block my listbox so that when the User gives the same name in TextBox that it reject it.in C#

2. My second request is about a ArrayList.

-I have without problem insert a list of evenement or action(for example: StandUP,Sleep,Eat,Work, answer ) in my Arraylist but i don't know how to make a Link or Relation between a diifferent action. I ask to sombody in the college he speak about a Tological Sort(). I don't no one thing about it.

Please I found one algorithm about it. But to transform it in C# language is so difficult for me.
Here is the Algorithme

Calculate network(working-packages A = {wP1..., wPn}, dependence Dep ⊂ A × A)
  A' ← TOPOLOGICAL-SORT(A,Dep)
  (now all dependent WPs stand behind their(her) presuppositions)
  for WP ∈ A' (in accordance with topological order)
  do ⌈ if WP is the first task   
    then [ EarliestBegin(WP) ← 0
       else [ EarliestBegin(WP) ← max X ∈ WP mit (X,WP) ∈ Dep : EarliestEnds(X)
     ⌊ EarliestEnds(WP) ← EarliestBegin(WP) + Duration(WP)
  for WP ∈ A' (in accordance with reverse topological order)
  do ⌈ if WP is Last Task      
    then [ LaterEnds(WP) ← maximum project duration (or  EarliestEnds(WP))
       else [ LaterEnds(WP) ← min X ∈ WP mit (WP,X) ∈ Dep : LaterBegin(X)
     ⌊ LaterBegin(WP) ← LaterEnd(WP) - Duration(WP)

Can someboy Help me to understand it maybe to explain me the different step please. the code i will try firstly for myself.

Please how can i understand interpretate it
thanks in advance
Leonce

Tags: C# (C# 4.0), SQL Server, Windows Forms, SQL Server 2008