FileStore.setSeqNum() not disposing StreamWriter

[josephlam]

    private void setSeqNum()
    {
        seqNumsFile_.Seek(0, System.IO.SeekOrigin.Begin);
        System.IO.StreamWriter writer = new System.IO.StreamWriter(seqNumsFile_);

        writer.Write(GetNextSenderMsgSeqNum().ToString("D10") + " : " + GetNextTargetMsgSeqNum().ToString("D10") + "  ");
        writer.Flush();
    }

writer isn't closed/disposed. Should wrap in a using() block.
Since .Net 4.5 it's possible to dispose StreamWriter without closing the underlying stream:
https://connect.microsoft.com/VisualStudio/feedback/details/164680/streamwriter-incorrectly-disposes-underlying-stream
Or maybe it should be keeping the StreamWriter in the seqNumsFile instance variable instead of the underlying FileStream.