Currently, the print preview control provides only options for the current printer, the page orientation and the page size . Include the following options too:

 - Paper Format (Lettre, A4, etc.)
 - Paper Orientation (Portrait or Landscape)
 - Number of copies (1, 2, 3, ...)
 - Print Color Settings (Colors or Monochrome)
 - Margins
 - Resolution (DPI based on the capabilities of the printer)

Add an option to modify the StartPoint and EndPoint properties of RadDiagramConnection instances via the SettingsPane.

This functionality can be achieved by modifying the default ControlTemplate of the SettingsPaneView element to include an additional RadTabItem instance in the RadTabControl element. In the additional RadTabItem, input controls can be used, such as the RadNumericUpDown element. These elements should modify properties that will be present in a custom LinkViewModelBase<NodeViewModelBase>> class. More specifically, the X and Y properties of the StartPoint and EndPoint properties of the RadDiagramConnection element.

The attached sample project shows the implementation of the above approach for achieving this requirement.

Add an option to customize the available colors in the SettingsPane control:

Implement support (or extensibility) for printing the whole diagram in a single page.

Currently large diagrams are hard to export with good quality because of the memory limitation in WritableBitmap when the DPI is increased.

 -- One option is to use BitMapCacheBrush (discussed here http://www.telerik.com/forums/low-resolution-using-exporttoimage-on-big-diagram)

 -- Another option is to export multiple images of the diagram which cover it all. Then possibly combine these pictures into one.

 -- Also , you can try increasing the operating memory of your Visual Studio

Currently, the content of RadDiagramShape element alignment can be changed via its HorizontalContentAlignment and VerticalContentAlignment. However, in RadDiagramTextShape, those properties don't take effect. Instead the text content is always centered.

At this point, you can achieve this requirement, by extracting the ControlTemplate of RadDiagramTextShape and bind the corresponding properties of the ContentPresenter to the parent shape. For example:

<ContentPresenter x:Name="NormalContent"
				  Margin="{TemplateBinding Padding}"
				  HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
				  VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>

I looked at the RadDiagram options, but it doesn't have anything that compares to a circular relationship chart.  Here's an example:

https://www.codeproject.com/KB/silverlight/342715/screenshot2.png

Part of this article:

https://www.codeproject.com/Articles/342715/Plotting-Circular-Relationship-Graphs-with-Silverl

I gave some thought at trying to rewrite the code into WPF, but I've got too many other irons in the fire.  Figured I'd ask as this sort of visualization control doesn't appear in your current collection.  I have a project that could benefit from displaying weighted relationships in such a manner, but my choices are either do something sub-par with the RadDiagram option, write one myself, find another controls collection and port everything, or leave the feature out for now.  I'm going for the leave it out option for the moment, and see if your UI wizards can come up with something...

Just as a use case, one of the reasons for wanting this is to diagram conversations between individuals in email messages.  Being able to show who's talking to whom and how frequently using one of these charts for visualization allows you to quickly find patterns...

When zooming out on more than 500-600 shapes and then panning, if telerik:DiagramSurface.IsVirtualizing="True", the performance is slower. 

When virtualization is off, the performance is a little better.

Connect the Diagrams BackgroundGrid to the Ruler's Measurement Unit and ScaleDefinitions.

Currently only in DPI measurement unit the scaledefinitions and diagram background grid look good and consistent.

A possible workaround is to use an attached property. Basically, we've added ConnectionPointsProperty in AttachedProperties class and added binding to this new property in the style of the connection.

public class AttachedProperties
    {
        public static RadDiagram Diagram { get; set; }

        public static readonly DependencyProperty ConnectionPointsProperty =
           DependencyProperty.RegisterAttached("ConnectionPoints", typeof(List<Point>), typeof(AttachedProperties), new PropertyMetadata(null, OnConnectionPointsChanged));

        public static IEnumerable<Point> GetConnectionPoints(DependencyObject obj)
        {
            return (IEnumerable<Point>)obj.GetValue(ConnectionPointsProperty);
        }

        public static void SetConnectionPoints(DependencyObject obj, IEnumerable<Point> value)
        {
            obj.SetValue(ConnectionPointsProperty, value);
        }

        private static void OnConnectionPointsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var connection = d as RadDiagramConnection;
            var connectionPoints = e.NewValue as List<Point>;
            if (connection != null && connectionPoints != null)
            {
                for (int i = 0; i <  connectionPoints.ToList().Count; i++)
                {
                    connection.ConnectionPoints.Add(connectionPoints.ToList()[i]);                 
                }
                connection.IsModified = true;
                (connection as IConnection).Update();
            }
        }
    }



  <telerik:RadDiagram.ConnectionStyle>
                <Style TargetType="telerik:RadDiagramConnection">
                    <Setter Property="ConnectionType" Value="Polyline"/>
                    <Setter Property="local:AttachedProperties.ConnectionPoints" Value="{Binding MyConnectionPoints}"/>
                </Style>
            </telerik:RadDiagram.ConnectionStyle>

You should be able to prevent the horizontal/vertical overlapping of routed connections . This way the connections should be easier to differentiate.

To better differentiate connections, users might:

            --- use labels on the connections

            --- use bezier connections

            --- use different colors for different connections

            --- use more custom connectors and attach the connections to not used connectors

            -- use AStartRouter instead of the default one (Grid Router)

Be able to pre-select, printer, page size and page orientation in the RadDiagramPrintPreview. By default, RadDiagramPrintPreview set the printing orientation in landscape even if we created a diagram in portrait.