Use the Item property to access to a specific column.  The Count property counts the columns in the control. Use the Columns property to access the control's Columns collection.

The following VB sample enumerates the columns in the control:

For Each c In Tree1.Columns
    Debug.Print c.Caption
Next

The following VB sample enumerates the columns in the control:

For i = 0 To Tree1.Columns.Count - 1
    Debug.Print Tree1.Columns(i).Caption
Next

The following VC sample enumerates the columns in the control:

#include "Columns.h"
#include "Column.h"
CColumns columns = m_tree.GetColumns();
for ( long i = 0; i < columns.GetCount(); i++ )
{
	CColumn column = columns.GetItem( COleVariant( i ) );
	OutputDebugString( column.GetCaption() );
}

The following VB.NET sample enumerates the columns in the control:

With AxTree1.Columns
    Dim i As Integer
    For i = 0 To .Count - 1
        Debug.WriteLine(.Item(i).Caption)
    Next
End With

The following C# sample enumerates the columns in the control:

EXTREELib.Columns columns =axTree1.Columns;
for ( int i = 0; i < columns.Count - 1; i++ )
{
	EXTREELib.Column column = columns[i];
	System.Diagnostics.Debug.WriteLine( column.Caption );
}

The following VFP sample enumerates the columns in the control:

with thisform.Tree1.Columns
	for i = 0 to .Count - 1
		wait window nowait .Item(i).Caption
	next
endwith