[DefaultValue(0)]
public double Value { get; set; }

<DefaultValue(0)>
Public Property Value As Double

// Create a storage to provide data for the vector layer.
private IMapDataAdapter CreateData() {
    MapItemStorage storage = new MapItemStorage();

    // Add Bubble charts with different values, sizes and 
    // locations to the storage's Items collection.
    storage.Items.Add( new MapBubble() {
        Argument = "A",
        Value = 200,
        Location = new GeoPoint(-45, -60),
        Size = 20,
        Group = 1,
        MarkerType = MarkerType.Diamond
    });
    storage.Items.Add( new MapBubble() {
        Argument = "B",
        Value = 400,
        Location = new GeoPoint(-45, 0),
        Size = 40,
        Group = 2,
        MarkerType = MarkerType.Plus
    });
    storage.Items.Add( new MapBubble() {
        Argument = "C",
        Value = 800,
        Location = new GeoPoint(-45, 60),
        Size = 80,
        Group = 1,
        MarkerType = MarkerType.Cross
    });

    return storage;
}

' Create a storage to provide data for the vector layer.
Private Function CreateData() As IMapDataAdapter
    Dim storage As New MapItemStorage()

    ' Add Bubble charts with different values, sizes and 
    ' locations to the storage's Items collection.
    storage.Items.Add(New MapBubble() With {.Argument = "A", .Value = 200, .Location = New GeoPoint(-45, -60), .Size = 20, .Group = 1, .MarkerType = MarkerType.Diamond})
    storage.Items.Add(New MapBubble() With {.Argument = "B", .Value = 400, .Location = New GeoPoint(-45, 0), .Size = 40, .Group = 2, .MarkerType = MarkerType.Plus})
    storage.Items.Add(New MapBubble() With {.Argument = "C", .Value = 800, .Location = New GeoPoint(-45, 60), .Size = 80, .Group = 1, .MarkerType = MarkerType.Cross})

    Return storage
End Function