C#查询datatable接收数据集并转换为json返回

 StringBuilder commandText = new StringBuilder();
commandText.Append("select clientcode,coperator, skdate,usefund,skway,skprice from ReceiptLog");
commandText.Append(" WHERE clientcode = '"+Custcode+"'");
SysDBModel.CodeValue Codeobj = new SysDBModel.CodeValue();
DataTable CodeTable = new DataTable();
Codeobj.ExecuteQuery(commandText.ToString(), CodeTable);
var jsonString = new StringBuilder();
if (CodeTable.Rows.Count > 0)
{
    jsonString.Append("[");
    for (int i = 0; i < CodeTable.Rows.Count; i++)
    {
        jsonString.Append("{");
        for (int j = 0; j < CodeTable.Columns.Count; j++)
        {
            if (j < CodeTable.Columns.Count - 1)
            {
                jsonString.Append("\"" + CodeTable.Columns[j].ColumnName.ToString()
                + "\":" + "\""
                + CodeTable.Rows[i][j].ToString() + "\",");
            }
            else if (j == CodeTable.Columns.Count - 1)
            {
                jsonString.Append("\"" + CodeTable.Columns[j].ColumnName.ToString()
                + "\":" + "\""
                + CodeTable.Rows[i][j].ToString() + "\"");
            }
        }
        if (i == CodeTable.Rows.Count - 1)
        {
            jsonString.Append("}");
        }
        else
        {
            jsonString.Append("},");
        }
    }
    jsonString.Append("]");
}
return jsonString.ToString();
return "OK";