empty points

Hello, How can I add empty points (missing values) to line or bar series? Please write an example in Visual Basic language. Thanks

The bar and line series both detect a variety of empty points and other data types. As the Nothing keyword in vb.net represents the default value you need to set the generic type that your data collection holds to be nullable:

Private Data As ObservableCollection(Of Point?)

Null values in your collection will then be detected and displayed appropriately. Shown here are a few ways your null data could be represented, with a null point, a point containing null data, the Y value being NotANumber, and the X value being null, respectively:

For j As Integer = 1 To 30
      If j = 5 Then
        Data.Add(Nothing)          
      ElseIf j = 11 Then
        Data.Add(New Point?(Nothing))
      ElseIf j = 15 Then
        Data.Add(New Point(j, Double.NaN))
      ElseIf j = 19 Then
        Data.Add(New Point(Nothing, rnd.Next(2, 10)))
      Else
        Data.Add(New Point(j, rnd.Next(2, 10)))
      End If
Next

This will of course work where Data is bound to the ItemsSource of a BarSeries or LineSeries. The former will display an empty missing bar along the X axis, while the LineSeries will show a gap in the line.

Note that this also applies to other data types that can be in your Collection - we support drawing charts from a wide range of other types like collections of ints/doubles as well as our built-in DateTimeDouble and StringDouble types. As long as the '?' operator is used after the type any objects in these can be null and they will be displayed properly.

Thank you for your response. The barseries is correct, but the line series is not. What is wrong?

Ah, the LineSeries supports the following forms of null data items:

Data.Add(Nothing)

Data.Add(New Point(j, Double.NaN))

The other two (in the case where j = 11 and j = 19 in your screenshot) will work for BarSeries, but not for LineSeries.