Autosize ListView Columns

While browsing through Windows Management Instrumentation scripting samples (more on using WMI to track down network configurations later), I ran into an interesting bit of code in this otherwise unrelated sample on VBnet. Buried in the sample is a snippet showing how to autosize the columns of a ListView control in Report mode using the SendMessage API. This may be old news to everyone else, but I was glad to see it, and the timing was perfect.

I'd like to show you the relevant parts of the sample's code, but the author, Randy Birch, has unfortunately decided that I "may not reproduce or publish this code on any web site, online service, or distribute as source on any media without express permission." Okay. Well, I'm not going to call Mr. Birch at this hour to get his permission, so I guess I'll show you how I use the technique in my code.

Private Declare Function SendMessage _
                Lib "user32" _
                Alias "SendMessageA" _
                (ByVal hwnd As Long, _
                 ByVal wMsg As Long, _
                 ByVal wParam As Long, _
                 lParam As Any) As Long

Private Sub AutosizeColumns(ByVal TargetListView As ListView)

  Const SET_COLUMN_WIDTH    As Long = 4126
  Const AUTOSIZE_USEHEADER  As Long = -2

  Dim lngColumn As Long

  For lngColumn = 0 To (TargetListView.ColumnHeaders.Count - 1)
   
    Call SendMessage(TargetListView.hwnd, _
                     SET_COLUMN_WIDTH, _
                     lngColumn, _
                     ByVal AUTOSIZE_USEHEADER)
        
  Next lngColumn

End Sub

Please pardon the excessive line-continuations. I'm trying to avoid cutting off code samples at lower resolutions.

This technique offers a couple of real bonuses. First, it sizes columns to the wider of the ColumnHeader.Text or the widest ListSubItem.Text. Second, the last column is automatically sized to the remaining ListView width, if it's larger than the column's header or widest value. Cool. Maybe there's an easier way to accomplish this in VB6, but I don't know what it is.

By the way, the ListView control has changed in .NET (see System.Windows.Forms.ListView). It now exposes a Columns property containing a collection of ColumnHeader objects, and these now expose a Width property that can be set to adjust the width at runtime. Specifically, -1 sets the width to the widest column text, while -2 sets the width to the larger of the column header text or the remaining ListView width (which is cool, but still doesn't get you a complete autosize as above, which considers the column text, column header text, and remaining ListView width).

Here's an interesting Code Project article by Chris Beckett that improves on the new .NET ListView options by causing the last column to autosize with any ListView control size change. Note that it is Mr. Beckett who points out that a Width of -2 gets you the remaining ListView width behavior; the MS documentation doesn't mention it.