Though my previous post get deleted I'll try to give more complex answer on the question.
The topmost answer is not quite actual anymore as the Graph# library is strongly outdated.
I'll recommend to check the combination of GraphX and Quickgraph. GraphX as the rendering engine and Quickgraph as the graph management and math operation component.
GraphX library is coded for WPF 4.0 and METRO. It provides many features that Graph# lacks:
- Improved rendering performance for large graphs
- Edge routing and bundling support, many other edge options
- Enhanced zoom control which supports Overview window and multiple vertices selection
- Rich documentation and samples
Also GraphX supports all the original layout algorithms from Graph#.