Array.BinarySearch does not work

Question

Hi!! I am having this strange problem. I have a sorted array containing strings. I am iterating through the array and clearing the contents one by one using array.BinarySearch to find each element. So far so good. But the moment I come to the last element the BinarySearch method fails.It gives me a return value which is negative although the element is very much there. I am debugging through the code and I find nothing wrong with it.Note that i am using the first overloaded method of BinarySearch which accepts the name of the array and the value. Any little help would be highly appreciated since this is very very urgent. Thanks all of you in advance.

yogeshmanohar · Answer

Thanks very much for your help all the same.I really do appreciate the efforts that you put in for me.

joy.simpson · Answer

Sorry. I'm just beginning to get a handle on the basics and haven't progressed far beyond Console applications. Your code is too complex for me right now. Maybe someone else can help.

yogeshmanohar · Answer

Hi !! Thanks a million for taking so many efforts !!! I did try out your sample and it worked great ! When I compared your code to mine I found that it is on similar grounds. But I feel the problem lies somewhere in the fact that I am iterating backwards. This is because I am storing the names of the controls (in a panel) into the array and depending on these names I am removing the controls one by one and setting each element to nothing in the array. This all works really fine except when it comes the last iteration ie the first element in the array it fails . Can I request you please have a look at my code and tell me whats wrong?? It might be slightly complicated to understand since you dont have the background as to what I am trying to do in the first place..but I will try to explain. 'strPBNames = Array name declared at module level : Private strPBNames(0) As String 'panThumb = Panel which holds a series of pictureboxes (pb0 pb1pb2 etc) 'blnSelectAll = If all the controls are selected by pressing the Select All button strPBNames.Sort(strPBNames) intControlCount = panThumb.Controls.Count - 1 For intctr = intControlCount To 0 Step -1 If blnSelectAll = True Then RemoveHandler panThumb.Controls(intctr).Click AddressOf pb_Click RemoveHandler panThumb.Controls(intctr).MouseDown AddressOf pb_MouseDown panThumb.Controls.RemoveAt(intctr) Else If strPBNames.BinarySearch(strPBNames panThumb.Controls(intctr).Name) >= 0 Then intIndex = strPBNames.IndexOf(strPBNames panThumb.Controls(intctr).Name) RemoveHandler panThumb.Controls(intctr).Click AddressOf pb_Click RemoveHandler panThumb.Controls(intctr).MouseDown AddressOf pb_MouseDown panThumb.Controls.RemoveAt(intctr) strPBNames.Clear(strPBNames intIndex 1) End If End If Next The reason why I have to iterate backwards is because the controls in a panel are always in a collection.So if you start iterating from the first control and remove it the indexes of all the other controls change and therefore the loop fails !! It will be really great if you can figure out what the problem is !! I am really foxed at this one!! Thanks Again.

joy.simpson · Answer

Sorry. The sample I gave you above is in C#. I didn't realize I was in the VB thread. I did it over again in VB using a string array and it works. The user enters 12 strings which are saved to an array. The array is sorted and displayed. Then the user selects a string and the BinarySearch will display the array index if found or tell the user if not found. Module Module1 Sub Main() Dim x find As Integer target As String Dim stary(12) As String For x = 1 To 12 Console.Write({0}:  x) stary(x) = Console.ReadLine() Next x Array.Sort(stary) Console.WriteLine() For x = 1 To 12 Console.Write({0}  stary(x)) Next x Do Console.Write(vbLf & vbLf & Enter a string to search for or nothing to stop: ) target = Console.ReadLine() find = Array.BinarySearch(stary target) If find  Then Console.Write(vbLf & {0} was not found.  target) ElseIf target  Then Console.Write(vbLf & {0} was found at stary({1})  target find) End If Loop While target  Console.WriteLine() End Sub End Module

joy.simpson · Answer

Here's a working sample. It starts out with a sorted array of 35 random numbers which are displayed for the user to see. User then selects a number. BinarySearch locates and displays the array position if the number is found or lets the user know if it is not found. I haven't tried this with a string array so maybe that works differently. But check out this code anyway. using System; namespace BiSearch_CS { class Class1 { static void Main(string[] args) { int x target find addrnd; int[] numary = new int[36]; Random randnum = new Random(); for (x = 1; x <= 35; x++) { addrnd = randnum.Next(1 6); numary[x] = numary[x - 1] + addrnd; Console.Write({0}  numary[x]); } Console.Write(

Enter a number to search for or 0 to stop: ); do { try { target = Convert.ToInt32(Console.ReadLine()); } catch { target = 0; } find = Array.BinarySearch(numary target); if (find < 0 & target != 0) Console.Write(
{0} was not found.  target); else if (target != 0) Console.Write(
{0} was found at myarray[{1}]  target find); } while (target != 0); Console.WriteLine(); } } }