テキストファイルから重複行＋NGワード削除≪Hashtable編≫

try
{
    StreamReader sr = null;
    string s;
    Hashtable ngHash = new Hashtable();
    //NGデータのHashtable作成
    try
    {
        sr = new StreamReader(@"C:\temp\ngdata.txt", Encoding.GetEncoding(932));
        while ((s = sr.ReadLine()) != null) { ngHash[s] = true; }
    }
    finally
    {
        if (sr != null) sr.Close();
    }
    //出力データを作成
    sr = null;
    ArrayList al = new ArrayList();
    try
    {
        sr = new StreamReader(@"C:\temp\data.txt", Encoding.GetEncoding(932)); 
        Hashtable uniqHash = new Hashtable();
        while ((s = sr.ReadLine()) != null)
        {
            if (uniqHash[s] == null)
            {
                uniqHash[s] = true;
                if (ngHash[s] == null) { al.Add(s); }
            }
        }
    }
    finally
    {
        if (sr != null) sr.Close();
    }
    //ソート
    al.Sort();
    //出力
    StreamWriter sw = null;
    try
    {
        sw = new StreamWriter(@"C:\temp\output.txt", false, Encoding.GetEncoding(932));
        for (int i=0; i<al.Count; i++) { sw.WriteLine(al[i]); }
    }
    finally
    {
        if (sw != null) sw.Close();
    }
}
catch(Exception ex)
{
    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); 
}