How to move selected node using Arrow keys ?

Arrow.Left
Arrow.Right
Arrow.Up
Arrow.Down

I added following command binding in constructor

diagram.CommandBindings.Add(new CommandBinding(Diagram.NavigateLeft,
                (sender, args) =>
                { DiagramNode node = diagram.ActiveItem as DiagramNode;
                    if (node != null)
                    {
                        node.Move(node.Bounds.Left - 10, node.Bounds.Top);
                    }

                })); 

once I added that and put item on to canvas I can move item to left side using Arrow.Left Key , other keys not working here.

okay now that working fine, but there is small issue , once I select an item, an move it. I can move it over(out of) the defined canvas, I want to restrict that , how can I do that

here the pic of it

as you guided, for all arrow key operations

I composed following code,

but only the  "left arrow handler" working  here

            // left arrow handler
            diagram.CommandBindings.Add(
            new CommandBinding(Diagram.NavigateLeft, (sender, args) =>
            {
            DiagramNode node = diagram.ActiveItem as DiagramNode;
            if (node.Bounds.Left - 10 >= diagram.Bounds.Left)
                node.Move(node.Bounds.Left - 10, node.Bounds.Top);

            }));

            // right arrow handler
            diagram.CommandBindings.Add(
            new CommandBinding(Diagram.NavigateRight, (sender, args) =>
            {
                DiagramNode node = diagram.ActiveItem as DiagramNode;
                if (node.Bounds.Right - 10 >= diagram.Bounds.Right)
                    node.Move(node.Bounds.Right - 10, node.Bounds.Top);
            }));

            // up arrow handler
            diagram.CommandBindings.Add(
            new CommandBinding(Diagram.NavigateUp, (sender, args) =>
            {
                DiagramNode node = diagram.ActiveItem as DiagramNode;
                if (node.Bounds.Top - 10 >= diagram.Bounds.Top)
                    node.Move(node.Bounds.Top - 10, node.Bounds.Top);
            }));

            // down arrow handler
            diagram.CommandBindings.Add(
            new CommandBinding(Diagram.NavigateDown, (sender, args) =>
            {
                DiagramNode node = diagram.ActiveItem as DiagramNode;
                if (node.Bounds.Bottom - 10 >= diagram.Bounds.Bottom)
                    node.Move(node.Bounds.Bottom - 10, node.Bounds.Bottom);
            }));
 

up arrow key function and down arrow key functions still not working properly

now this is working for individual items, once I group few nodes and try to move using arrow keys , I want to move those all elements as a group, but currently its moving only last selected item, how can I resolve this ?

As you said I changed following code

var node = diagram.ActiveItem as DiagramNode; 

To

 var node = diagram.Selection.Nodes as DiagramNodeCollection;; 

but then having following error

Cannot convert type 'DiagramNodeCollection' does not contain a definition for 'Bounds' and no extension method 'Bounds' accepting a first argument of type 'DiagramNodeCollection'

'DiagramNodeCollection' does not contain a definition for 'Move' and no extension method 'Move' accepting a first argument of type 'DiagramNodeCollection' could be found

thanks for the continues support, I have another problem related to this scenario,

Once moving Nodes using arrow keys, I want to restrict overlap scenarios also

these are the steps for that scenario

1. select a Node
2. move that using arrow key,  
     if
its overlapping with existing node, revoke that move at reset to previous location.

else
    allow to move that node

Thnks
Kelum