Add Group Collapse Behavior on a Listview Control

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Introduction

ListView control is an important but complex control in the WinForm environment. Group behavior is added into this control, but unfortunately, we can't collapse or expand the group.

I'll show how to use some simple code to add collapse/expand behavior on the ListView control.

This is a sample image on Windows Vista and Windows Server 2008:

Using the Code

• Define ListView group struct wrapper:

  C#

  [StructLayout(LayoutKind.Sequential)] 
  public struct LVGROUP 
  { 
          public int cbSize; 
          public int mask; 
          [MarshalAs(UnmanagedType.LPTStr)] 
          public string pszHeader; 
          public int cchHeader; 
          [MarshalAs(UnmanagedType.LPTStr)] 
          public string pszFooter; 
          public int cchFooter; 
          public int iGroupId; 
          public int stateMask; 
          public int state; 
          public int uAlign; 
  } 

• Define the ENUM data:

  C#

  public enum GroupState 
  { 
          COLLAPSIBLE = 8, 
          COLLAPSED = 1, 
          EXPANDED = 0 
  } 

• Interop for SendMessage function:

  C#

  [DllImport("user32.dll")] 
  static extern int SendMessage
  	(IntPtr window, int message, int wParam, IntPtr lParam);

• Kernel method to set collapse/expand behavior on the ListView group:

  C#

  private void SetGroupCollapse(GroupState state)
  {
          for (int i = 0; i <= aoc.Groups.Count; i++){
                  LVGROUP group = new LVGROUP();
                  group.cbSize = Marshal.SizeOf(group);
                  group.state = (int)state; // LVGS_COLLAPSIBLE 
                  group.mask = 4; // LVGF_STATE 
                  group.iGroupId = i;
                  IntPtr ip = IntPtr.Zero;
                  try{
                          ip = Marshal.AllocHGlobal(group.cbSize);
                          Marshal.StructureToPtr(group, ip, true);
                          SendMessage(aoc.Handle, 0x1000 + 147, i, ip); // #define
                          LVM_SETGROUPINFO (LVM_FIRST + 147) 
                  }
                  catch (Exception ex){
                          System.Diagnostics.Trace.WriteLine
  			(ex.Message + Environment.NewLine + ex.StackTrace);
                  }
                  finally{
                          if (null != ip) Marshal.FreeHGlobal(ip);
                  }
         }
  } 

Points of Interest

#define LVM_SETGROUPINFO (LVM_FIRST + 147)
#define ListView_SetGroupInfo(hwnd, iGroupId, pgrp) \
SNDMSG((hwnd), LVM_SETGROUPINFO, (WPARAM)(iGroupId), (LPARAM)(pgrp)) 

The above is the definition from SDK file: commctrl.h.

Limitations

• In the current version, the rightmost collapse/expand icon doesn't work. :(
• The collapse/expand behavior only exist in Windows Vista and Win2k8 systems.

History

• 27^th November, 2008: Initial post