This code tells you the Partition's Range Keys (High and Low) of your current partition in a Service Fabric Stateful Reliable Service

ServiceFabricPartitionRangeKeys.cs

// This code can run in any Azure Service Fabric Stateful Reliable Service 
// within the method protected override async Task RunAsync(CancellationToken cancellationToken)
//Aditional or similar code in: https://github.com/Azure-Samples/service-fabric-dotnet-getting-started/blob/master/Services/WordCount/WordCount.WebService/Controllers/DefaultController.cs

                var fabricClient = new FabricClient();
                string serviceUri = "fabric:/MySFApp/MyStatefulService";
                Uri serviceUriInstance = new Uri(serviceUri);

                System.Fabric.Query.ServicePartitionList partitionList = 
                                                await fabricClient.QueryManager.GetPartitionListAsync(serviceUriInstance);

                foreach (var partition in partitionList)
                {
                    if(partition.PartitionInformation.Id == this.Context.PartitionId)
                    {
                        if (partition.PartitionInformation.Kind == ServicePartitionKind.Int64Range)
                        {
                            Int64RangePartitionInformation currentInt64RangePartition = (Int64RangePartitionInformation)partition.PartitionInformation;
                            
                            ServiceEventSource.Current.ServiceMessage(this, "Partition ID: {0} -- HighKey: {1} -- LowKey: {2}", 
                                                                            this.Context.PartitionId, 
                                                                            currentInt64RangePartition.HighKey, 
                                                                            currentInt64RangePartition.LowKey);
                        }
                        else
                        {
                            ServiceEventSource.Current.ServiceMessage(this, "Partition is not Int64Range");
                        }
                    }
                }