删除List<string>中重复的值

public void getList()
    {
        List<string> outPut=new List<string>();
        outPut.Add("ad");
        outPut.Add("ac");
        outPut.Add("aa");
        outPut.Add("ac");
        for (int i = 0; i < outPut.Count; i++)
        {
            for (int j = i + 1; j < outPut.Count; j++)
            {

                if (outPut[i].ToString().Equals(outPut[j].ToString()))
                {
                    outPut.Remove(outPut[j].ToString());
                }
            }
        }
        foreach (string str in outPut)
        {
            Response.Write(str.ToString()+",");
        }
    }