public bool find(string keywords, string text)
{
    List<string> incList = new List<string>();
    List<string> excList = new List<string>();
    if (keywords.IndexOf("-") > -1)
    {
        string incKeys = keywords.Substring(0, keywords.IndexOf("-"));
        string excKeys = keywords.Substring(keywords.IndexOf("-") + 1);
        if (keywords.IndexOf("+") > -1)
        {
            if (incKeys.IndexOf("+") > -1)
                incList = new List<string>(incKeys.Split('+'));
            else
                incList.Add(incKeys);
        }
        if (excKeys.IndexOf("-") > -1)
            excList = new List<string>(excKeys.Split('-'));
        else
            excList.Add(excKeys);
    }
    else
    {
        if (keywords.IndexOf("+") > -1)
            incList = new List<string>(keywords.Split('+'));
        else
            incList.Add(keywords);
    }

    if (incList.Count > 0)
    {
        foreach (string s in incList)
        {
            if (text.IndexOf(s) == -1)
                return false;
        }
    }

    if (excList.Count > 0)
    {
        foreach (string s in excList)
        {
            if (text.IndexOf(s) > -1)
                return false;
        }
    }
    return true;
}

------解决方案--------------------
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