IEnumerator给出null异常，但不是null

我对.NET还很陌生，所以请耐心等待。

LinqToTwitter中的IEnumerable有一个奇怪的问题
查询返回一个IEnumerable，而Console.WriteLine表示它拥有两个post
但是，当我尝试在枚举器上调用MoveNext()时，我会得到一个空指针异常。

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代码

TwitterContext ctx = this.twitterContext;
IEnumerable<Status> statuses =
    from tweet in ctx.Status
        .AsEnumerable()
    select tweet;
IEnumerator<Status> eStat = statuses.GetEnumerator();
// The output is:
// System.Linq.Enumerable+WhereSelectEnumerableIterator`2[LinqToTwitter.Status,LinqToTwitter.Status]
// So this shows that the IEnumerable holds 2 status values
Console.WriteLine(eStat);
// This line gives the exception
// "Value cannot be null."
Boolean hasNext = eStat.MoveNext();

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感谢的帮助

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Stacktrace

   at System.Reflection.RuntimeMethodInfo.MakeGenericMethod(Type[] methodInstantiation)
   at LinqToTwitter.TwitterQueryProvider.Execute[TResult](Expression expression)
   at LinqToTwitter.TwitterQueryable`1.GetEnumerator()
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at Broadcast.TwitterFeed.Program.Main(String[] args) in C:'Daten'TFS-Workspace'GD-TOP'Broadcast'Broadcast.TwitterFeed.Service'Broadcast.TwitterFeed'Program.cs:line 20
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

IEnumerable<Status> statuses =
(from tweet in ctx.Status
select tweet).ToList();