将datatable转化为Json格式字符串

 /// 将datatable转化为Json格式字符串
        /// </summary>  
        /// <param name="dt"></param>  
        /// <returns></returns>  
        public static string CreateJsonToDataTable(System.Data.DataTable dt)
        {
            StringBuilder JsonString = new StringBuilder();

            if (dt != null && dt.Rows.Count > 0)
            {
                JsonString.Append("[");
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    JsonString.Append("{ ");
                    for (int j = 0; j < dt.Columns.Count; j++)
                    {
                        if (j < dt.Columns.Count - 1)
                        {
                            JsonString.Append("\""+dt.Columns[j].ColumnName.ToString() +"\":" + "\"" + dt.Rows[i][j].ToString() + "\",");
                        }
                        else if (j == dt.Columns.Count - 1)
                        {
                            JsonString.Append("\"" + dt.Columns[j].ColumnName.ToString() + "\":" + "\"" + dt.Rows[i][j].ToString() + "\"");
                        }
                    }
                    if (i == dt.Rows.Count - 1)
                    {
                        JsonString.Append("} ");
                    }
                    else
                    {
                        JsonString.Append("}, ");
                    }
                }
                JsonString.Append("]");
                return JsonString.ToString();
            }
            return null;
        }