利用Relations实现多DataTable的聚合

最新推荐文章于 2018-07-07 10:37:13 发布

转载最新推荐文章于 2018-07-07 10:37:13 发布 · 83 阅读

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原文链接：http://www.cnblogs.com/lne818/archive/2009/03/11/1409075.html

Code
/// <summary>
/// 对DataTable进行GroupBy操作
/// </summary>
/// <param name="p_table"></param>
/// <param name="p_key"></param>
/// <returns></returns>
private static DataTable GetTableByGroupBy(DataTable p_table, string p_key, string p_colname)
{
    //对DataTable进行Group by
    DataTable parTable = new DataTable();
    DataColumn key = new DataColumn();
    key.DataType = System.Type.GetType("System.String");
    key.ColumnName = "MC";
    parTable.Columns.Add(key);

    DataColumn avg = new DataColumn();
    avg.DataType = System.Type.GetType("System.Double");
    avg.ColumnName = "AVG";
    parTable.Columns.Add(avg);
    foreach (DataRow row in p_table.Rows)
    {
        if (parTable.Select(string.Format("mc='{0}'", row[p_key].ToString())).Length == 0)
        {
            parTable.Rows.Add(new object[] { row[p_key] })["mc"] = row[p_key].ToString();
        }
    }

    DataSet ds = new DataSet();
    DataTable childTable = p_table.Copy();
    childTable.TableName = "child";
    ds.Tables.Add(childTable);
    parTable.TableName = "par";
    ds.Tables.Add(parTable);
    ds.Relations.Add("partochild", parTable.Columns["mc"], childTable.Columns[p_key]);
    parTable.Columns["avg"].Expression = string.Format("avg(child(partochild).{0})", p_colname);

    return parTable;
}

转载于:https://www.cnblogs.com/lne818/archive/2009/03/11/1409075.html