reference to assembly 'System.Core

Topics: algorithm, bug
Mar 4, 2013 at 2:17 PM
hey guys,
I'm working on my project to solving my privious problem and i used this code :
UndirectedDijkstraShortestPathAlgorithm<string, Edge<string>> dijkstra = new UndirectedDijkstraShortestPathAlgorithm<string, Edge<string>>(graph, QuickGraph.Algorithms.AlgorithmExtensions.GetIndexer<Edge<string>, double>(edgeCost));
but i get this error with "UndirectedDijkstraShortestPathAlgorithm" highlighted :
Error   2   The type 'System.Func`2<T0,T1>' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Core, Version=, Culture=neutral, PublicKeyToken=7cec85d7bea7798e, Retargetable=Yes'.  C:\Users\mega\documents\visual studio 2010\Projects\Getenic\Getenic\Graph.cs    131
i set my framework on .Net Framework 4.
can someone tell me how to fix this please?