将DataTable转换为Json

public static string DataTableToJson(string key, DataTable dt){       StringBuilder stbJson= new StringBuilder();  //定义json字符串       son.Append("{\"" + key+ "\":[");       if (dt.Rows.Count > 0)       {          for (int i = 0; i < dt.Rows.Count; i++)          {             stbJson.Append("{");             for (int j = 0; j < dt.Columns.Count; j++)             {                stbJson.Append("\"" + dt.Columns[j].ColumnName.ToString() + "\":\"" + dt.Rows[i][j].ToString() + "\"");                    if (j < dt.Columns.Count - 1)                    {                        stbJson.Append(",");                    }                }                stbJson.Append("}");                if (i < dt.Rows.Count - 1)                {                     stbJson.Append(",");                }            }        }        stbJson.Append("]}");        return stbJson.ToString();    }}