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Determining which TabPage was clicked

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7 Jan 2012CPOL1 min read 29.9K   6   6
A binary search technique to determine which TabPage of a TabControl was clicked
One of the many little WinForms applications I am working on has a TabControl with a variable number of TabPages (perhaps many). I want to allow the user to click and drag a tab to reorder the TabPages. A quick look at the documentation revealed nothing, and a quick search online revealed that this is a common problem.

The situation is that TabPages don't receive mouse events, the TabControl (their parent) does, then you have to use methods of the TabControl to determine which TabPage was clicked.

I glanced at two articles here on The Code Project to see how others had implemented this, and they provided a good starting point, but (being me) I came up with my own solution.

What I want is to get the index of a TabPage on MouseDown and again on MouseUp.
At first, I implemented a simple iterative search for the TabPage, but today I realized that a binary search technique would be better (at least with a great number of TabPages), so I changed it to:

private static int
  System.Windows.Forms.TabControl TabControl
  System.Drawing.Point            Point
  int result = -1 ;

  if ( TabControl != null )
    int lo = 0 ;
    int hi = TabControl.TabPages.Count - 1 ;

    while ( ( result == -1 ) && ( lo <= hi ) )
      int mid = lo + ( hi - lo ) / 2 ;
      System.Drawing.Rectangle rect = TabControl.GetTabRect ( mid ) ;

      if ( rect.Contains ( Point ) )
        result = mid ;
      else if ( ( Point.X < rect.Left ) || ( Point.Y < rect.Top ) )
        hi = mid - 1 ;
        lo = mid + 1 ;

  return ( result ) ;

Edit: Added test of ( Point.Y < rect.Top ) to handle left-aligned tabs -- but it still only works with one row or columns of Tabs.


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By
Software Developer (Senior)
United States United States
BSCS 1992 Wentworth Institute of Technology

Originally from the Boston (MA) area. Lived in SoCal for a while. Now in the Phoenix (AZ) area.

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Comments and Discussions

GeneralThe method fails if the TabControl.Multiline is set true and... Pin
Lutosław3-Jan-12 2:35
Lutosław3-Jan-12 2:35 
GeneralRe: Thanks, I didn't know there was such a thing. Pin
PIEBALDconsult3-Jan-12 3:50
mvePIEBALDconsult3-Jan-12 3:50 
GeneralRe: It also didn't work with System.Windows.Forms.TabAlignment.L... Pin
PIEBALDconsult4-Jan-12 15:52
mvePIEBALDconsult4-Jan-12 15:52 
GeneralHi, again completely OT, <a href=" Pin
thatraja10-Nov-11 19:11
professionalthatraja10-Nov-11 19:11 
GeneralSo, what happens if the click point is not in any of the rec... Pin
NeverJustHere8-Nov-11 17:59
NeverJustHere8-Nov-11 17:59 
GeneralRe: Basically, that never happens, but if you pass in a Point th... Pin
PIEBALDconsult8-Nov-11 18:23
mvePIEBALDconsult8-Nov-11 18:23 

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