// Create a new ChartControl instance.
ChartControl chart = new ChartControl();

// Create a series of a compatible view type, 
// and add it to the chart's collection,
// so the diagram object shall not to be equal to null.
Series series1 = new Series("Line Series 1", ViewType.Line);
chart.Series.Add(series1);

// Create a diagram, and cast it to the XYDiagram type.
XYDiagram diagram = (XYDiagram)chart.Diagram;

// Access the diagram's options.
diagram.Rotated = true;
diagram.DefaultPane.BackColor = Color.Aqua;

' Create a new ChartControl instance.
Dim chart As New ChartControl()

' Create a series of a compatible view type, 
' and add it to the chart's collection,
' so the diagram object shall not to be equal to Nothing.
Dim series1 As New Series("Line Series 1", ViewType.Line)
chart.Series.Add(series1)

' Create a diagram, and cast it to the XYDiagram type.
Dim diagram As XYDiagram = CType(chart.Diagram, XYDiagram)

' Access the diagram's options.
diagram.Rotated = True
diagram.DefaultPane.BackColor = Color.Aqua