C# Online Compiler | .NET Fiddle

<no name> by Anonymous

using System;
using System.Collections.Generic;
using System.Linq;
					
public class Program
{
	public static readonly IDictionary<int, IList<int>> dic = 
		new Dictionary<int, IList<int>>();
	
	public static void Main()
	{
		Enumerable
			.Range(1, 1000000)
			.AsParallel()
			.AsUnordered()
			.ForAll(i => AddValue(i % 100, i));
		
		Console.WriteLine($"Total Count: {dic.Sum(p => p.Value.Count)}");
		Console.WriteLine(
			$"Total Distinct Count: {dic.SelectMany(p => p.Value).Distinct().Count()}");
	}
	
	public static void AddValue(int kid, int vid)
	{
    	if(!dic.ContainsKey(kid))
			dic.Add(kid, new List<int>());
    	dic[kid].Add(vid);
	}
}

 
using System;
using System.Collections.Generic;
using System.Linq;
                    
public class Program
{
    public static readonly IDictionary<int, IList<int>> dic = 
        new Dictionary<int, IList<int>>();
    
    public static void Main()
    {
        Enumerable
            .Range(1, 1000000)
            .AsParallel()
            .AsUnordered()
            .ForAll(i => AddValue(i % 100, i));
        
        Console.WriteLine($"Total Count: {dic.Sum(p => p.Value.Count)}");
        Console.WriteLine(
            $"Total Distinct Count: {dic.SelectMany(p => p.Value).Distinct().Count()}");
    }
    
    public static void AddValue(int kid, int vid)
    {
        if(!dic.ContainsKey(kid))
            dic.Add(kid, new List<int>());
        dic[kid].Add(vid);
    }
}

Unhandled exception. System.AggregateException: One or more errors occurred. (Object reference not set to an instance of an object.) (Object reference not set to an instance of an object.) (The given key '1' was not present in the dictionary.) (The given key '4' was not present in the dictionary.)
---> System.NullReferenceException: Object reference not set to an instance of an object.
   at Program.AddValue(Int32 kid, Int32 vid)
   at Program.<>c.<Main>b__1_0(Int32 i)
   at System.Linq.Parallel.ForAllOperator`1.ForAllEnumerator`1.MoveNext(TInput& currentElement, Int32& currentKey)
   at System.Linq.Parallel.ForAllSpoolingTask`2.SpoolingWork()
   at System.Linq.Parallel.SpoolingTaskBase.Work()
   at System.Linq.Parallel.QueryTask.BaseWork(Object unused)
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
   --- End of inner exception stack trace ---
   at System.Linq.Parallel.QueryTaskGroupState.QueryEnd(Boolean userInitiatedDispose)
   at System.Linq.Parallel.SpoolingTask.SpoolForAll[TInputOutput,TIgnoreKey](QueryTaskGroupState groupState, PartitionedStream`2 partitions, TaskScheduler taskScheduler)
   at System.Linq.Parallel.DefaultMergeHelper`2.System.Linq.Parallel.IMergeHelper<TInputOutput>.Execute()
   at System.Linq.Parallel.MergeExecutor`1.Execute()
   at System.Linq.Parallel.MergeExecutor`1.Execute[TKey](PartitionedStream`2 partitions, Boolean ignoreOutput, ParallelMergeOptions options, TaskScheduler taskScheduler, Boolean isOrdered, CancellationState cancellationState, Int32 queryId)
   at System.Linq.Parallel.PartitionedStreamMerger`1.Receive[TKey](PartitionedStream`2 partitionedStream)
   at System.Linq.Parallel.ForAllOperator`1.WrapPartitionedStream[TKey](PartitionedStream`2 inputStream, IPartitionedStreamRecipient`1 recipient, Boolean preferStriping, QuerySettings settings)
   at System.Linq.Parallel.UnaryQueryOperator`2.UnaryQueryOperatorResults.ChildResultsRecipient.Receive[TKey](PartitionedStream`2 inputStream)
   at System.Linq.Parallel.ScanQueryOperator`1.ScanEnumerableQueryOperatorResults.GivePartitionedStream(IPartitionedStreamRecipient`1 recipient)
   at System.Linq.Parallel.UnaryQueryOperator`2.UnaryQueryOperatorResults.GivePartitionedStream(IPartitionedStreamRecipient`1 recipient)
   at System.Linq.Parallel.QueryOperator`1.GetOpenedEnumerator(Nullable`1 mergeOptions, Boolean suppressOrder, Boolean forEffect, QuerySettings querySettings)
   at System.Linq.Parallel.ForAllOperator`1.RunSynchronously()
   at Program.Main()
---> (Inner Exception #1) System.NullReferenceException: Object reference not set to an instance of an object.
   at Program.AddValue(Int32 kid, Int32 vid)
   at Program.<>c.<Main>b__1_0(Int32 i)
   at System.Linq.Parallel.ForAllOperator`1.ForAllEnumerator`1.MoveNext(TInput& currentElement, Int32& currentKey)
   at System.Linq.Parallel.ForAllSpoolingTask`2.SpoolingWork()
   at System.Linq.Parallel.SpoolingTaskBase.Work()
   at System.Linq.Parallel.QueryTask.BaseWork(Object unused)
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<---

---> (Inner Exception #2) System.Collections.Generic.KeyNotFoundException: The given key '1' was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at Program.AddValue(Int32 kid, Int32 vid)
   at Program.<>c.<Main>b__1_0(Int32 i)
   at System.Linq.Parallel.ForAllOperator`1.ForAllEnumerator`1.MoveNext(TInput& currentElement, Int32& currentKey)
   at System.Linq.Parallel.ForAllSpoolingTask`2.SpoolingWork()
   at System.Linq.Parallel.SpoolingTaskBase.Work()
   at System.Linq.Parallel.QueryTask.BaseWork(Object unused)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<---

---> (Inner Exception #3) System.Collections.Generic.KeyNotFoundException: The given key '4' was not present in the dictionary.
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at Program.AddValue(Int32 kid, Int32 vid)
   at Program.<>c.<Main>b__1_0(Int32 i)
   at System.Linq.Parallel.ForAllOperator`1.ForAllEnumerator`1.MoveNext(TInput& currentElement, Int32& currentKey)
   at System.Linq.Parallel.ForAllSpoolingTask`2.SpoolingWork()
   at System.Linq.Parallel.SpoolingTaskBase.Work()
   at System.Linq.Parallel.QueryTask.BaseWork(Object unused)
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(Thread threadPoolThread, ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)<---

Command terminated by signal 6

Last Run:	5:03:51 am
Compile:	0.019s
Execute:	0.23s
Memory:	6.97Mb
CPU:	0.249s

View IL Code