Public Function First() As KeyValuePair(Of TKey,TValue)

public KeyValuePair<TKey,TValue> First()

const int CountPerThread = 100;

BPlusTree<KeyInfo, DataValue>.OptionsV2 options = new BPlusTree<KeyInfo, DataValue>.OptionsV2(
    new KeyInfoSerializer(), new DataValueSerializer(), new KeyInfoComparer());
options.CalcBTreeOrder(32, 300);
options.FileName = TempFile.TempPath;
options.CreateFile = CreatePolicy.Always;

using (BPlusTree<KeyInfo, DataValue> dictionary = new BPlusTree<KeyInfo, DataValue>(options))
using (WorkQueue work = new WorkQueue(Environment.ProcessorCount))
{
    Exception lastError = null;
    work.OnError += delegate(object o, ErrorEventArgs e) { lastError = e.GetException(); };

    for (int i = 0; i < Environment.ProcessorCount; i++)
        work.Enqueue(new ThreadedTest(dictionary, CountPerThread).Run);

    for (int i = 0; i < CountPerThread; i++)
    {
        if(i%2 == 0)
        {
            try {
                dictionary.TryAdd(new KeyInfo(Guid.NewGuid(), i), k => { throw new ExpectedException(); });
            } catch { }
        }
        else
        {
            try
            {
                dictionary.TryRemove(dictionary.First().Key, (k, v) => { throw new ExpectedException(); });
            }
            catch { }
        }
    }

    Assert.IsTrue(work.Complete(true, 60000));
    Assert.IsNull(lastError, "Exception raised in worker: {0}", lastError);
}

Const  CountPerThread As Integer = 100

        Dim options As New BPlusTree(Of KeyInfo, DataValue).OptionsV2(New KeyInfoSerializer(), New DataValueSerializer(), New KeyInfoComparer())
        options.CalcBTreeOrder(32, 300)
        options.FileName = TempFile.TempPath
        options.CreateFile = CreatePolicy.Always

        Using dictionary As New BPlusTree(Of KeyInfo, DataValue)(options)
            Using work As New WorkQueue(Environment.ProcessorCount)
                Dim lastError As Exception = Nothing
                work.OnError += Function(o As Object, e As ErrorEventArgs) Do
                    lastError = e.GetException()
                End Function

                Dim i As Integer = 0
                While i < Environment.ProcessorCount
                    work.Enqueue(New ThreadedTest(dictionary, CountPerThread).Run)
                    System.Math.Max(System.Threading.Interlocked.Increment(i),i - 1)
                End While

                Dim i As Integer = 0
                While i < CountPerThread
                    If i Mod 2 = 0 Then
                        Try
                            dictionary.TryAdd(New KeyInfo(Guid.NewGuid(), i), Function(k) 
                            Throw New ExpectedException()

End Function)
                        Catch
                        End Try
                    Else
                        Try
                            dictionary.TryRemove(dictionary.First().Key, Function(k, v) 
                            Throw New ExpectedException()

End Function)
                        Catch
                        End Try
                    End If
                    System.Math.Max(System.Threading.Interlocked.Increment(i),i - 1)
                End While

                Assert.IsTrue(work.Complete(True, 60000))
                Assert.IsNull(lastError, "Exception raised in worker: {0}", lastError)
            End Using
        End Using