Datatable转换为Json 的方法

/// <summary>    
    /// Datatable转换为Json    
    /// </summary>   
    /// <param name="table">Datatable对象</param>    
    /// <returns>Json字符串</returns>    
    public static string ToJson(DataTable dt)
    {
        StringBuilder jsonString = new StringBuilder();
        jsonString.Append("[");
        DataRowCollection drc = dt.Rows;
        for (int i = 0; i < drc.Count; i++)
        {
            jsonString.Append("{");
            for (int j = 0; j < dt.Columns.Count; j++)
            {
                string strKey = dt.Columns[j].ColumnName;
                string strValue = drc[i][j].ToString();
                Type type = dt.Columns[j].DataType;
                jsonString.Append("\"" + strKey + "\":");
                strValue = StringFormat(strValue, type);
                if (j < dt.Columns.Count - 1)
                {
                    jsonString.Append(strValue + ",");
                }
                else
                {
                    jsonString.Append(strValue);
                }
            }
            jsonString.Append("},");
        }
        jsonString.Remove(jsonString.Length - 1, 1);
        jsonString.Append("]");
        return jsonString.ToString();
    }
    /// <summary>
    /// 格式化字符型、日期型、布尔型
    /// </summary>
    /// <param name="str"></param>
    /// <param name="type"></param>
    /// <returns></returns>
    private static string StringFormat(string str, Type type)
    {
        if (type == typeof(string))
        {
            str = String2Json(str);
            str = "\"" + str + "\"";
        }
        else if (type == typeof(DateTime))
        {
            str = "\"" + str + "\"";
        }
        else if (type == typeof(bool))
        {
            str = str.ToLower();
        }
        else if (type != typeof(string) && string.IsNullOrEmpty(str))
        {
            str = "\"" + str + "\"";
        }
        return str;
    }
    /// <summary>
    /// 过滤特殊字符
    /// </summary>
    /// <param name="s">字符串</param>
    /// <returns>json字符串</returns>
    private static string String2Json(String s)
    {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.Length; i++)
        {
            char c = s.ToCharArray()[i];
            switch (c)
            {
                case '\"':
                    sb.Append("\\\""); break;
                case '\\':
                    sb.Append("\\\\"); break;
                case '/':
                    sb.Append("\\/"); break;
                case '\b':
                    sb.Append("\\b"); break;
                case '\f':
                    sb.Append("\\f"); break;
                case '\n':
                    sb.Append("\\n"); break;
                case '\r':
                    sb.Append("\\r"); break;
                case '\t':
                    sb.Append("\\t"); break;
                default:
                    sb.Append(c); break;
            }
        }
        return sb.ToString();
    }