Count Property (Messages Collection)
The Count
property returns the number of Message objects in the collection, or a very large number
if the exact count is not available. Read-only.
Syntax
objMsgColl.Count
Data Type
Long
Remarks
The Count
property is useful for determining whether a Messages collection is empty or
not.
A large collection
cannot always maintain an accurate count of its members, and the Count
property cannot be used as the collection s size when it has a very large value
such as mapiMaxCount. Programmers needing to access individual objects
in a large collection are strongly advised to use the Visual Basic For Each
statement or the Get methods.
The
recommended procedures for traversing a large collection are, in decreasing
order of preference:
1. Global selection, such as the Visual Basic For
Each statement
2. The Get methods, particularly GetFirst and GetNext
3. An indexed loop, such as the Visual Basic For
... Next construction
If the
message store provider cannot supply the precise number of Message objects, the
OLE Messaging Library returns a very large number for the Count
property. On 32-bit platforms, this value is mapiMaxCount, which equals
2^31 - 1, or 2147483647. On other platforms, mapiMaxCount is not
defined, and the OLE Messaging Library returns -1. A program on such a
platform must be careful that -1 does not prematurely terminate any
iteration based on the Count property.
Programmers
using an indexed loop terminating on the Count property must also check
each returned object for a value of Nothing. The loop must proceed
forward from the beginning of the collection, and the index must have initial
and increment values of 1. Results are undefined for any other procedure.
The use of
the Item
property in conjunction with the Count property in a large collection
can be seen in the following example.
Example
This code
fragment searches for a Mesage object with subject Bonus :
Dim i As Integer ' loop index / object counter
Dim collMessages as Object ' Messages collection;
assume already given
If collMessages Is Nothing Then
' MsgBox
"Messages collection object is invalid"
' Exit
End If
' see if collection is empty
If 0 = collMessages.Count Then
' MsgBox
"No messages in collection"
' Exit
End If
' look for message about Bonus in collection
For i = 1 To collMessages.Count Step 1
If
collMessages.Item(i) Is Nothing Then
' MsgBox "No such message found in
collection"
' Exit '
no more messages in collection
End If
If
collMessages.Item(i).Subject = Bonus Then
' MsgBox
"Desired message is at index " & i
' Exit
End If
Next i