对datatable操作，查询

#region DataTable筛选，排序返回符合条件行组成的新DataTable或直接用DefaultView按条件返回
/// <summary>
/// DataTable筛选，排序返回符合条件行组成的新DataTable或直接用DefaultView按条件返回
/// eg:SortExprDataTable(dt,"Sex='男'","Time Desc",1)
/// </summary>
/// <param name="dt">传入的DataTable</param>
/// <param name="strExpr">筛选条件</param>
/// <param name="strSort">排序条件</param>
/// <param name="mode">1,直接用DefaultView按条件返回,效率较高;2,DataTable筛选，排序返回符合条件行组成的新DataTable</param>
public static DataTable SortDataTable(DataTable dt, string strExpr, string strSort, int mode)
{
    switch (mode)
    {
        case 1:
            //方法一　直接用DefaultView按条件返回
            dt.DefaultView.RowFilter = strExpr;
            dt.DefaultView.Sort = strSort;
            return dt;
        case 2:
            //方法二　DataTable筛选，排序返回符合条件行组成的新DataTable
            DataTable dt1 = new DataTable();
            DataRow[] GetRows = dt.Select(strExpr, strSort);
            //复制DataTable dt结构不包含数据
            dt1 = dt.Clone();
            foreach (DataRow row in GetRows)
            {
                dt1.Rows.Add(row.ItemArray);
            }
            return dt1;
        default:
            return dt;
    }
}
#endregion  

harp] view plaincopyprint?
#region 获取DataTable前几条数据
/// <summary>
/// 获取DataTable前几条数据
/// </summary>
/// <param name="TopItem">前N条数据</param>
/// <param name="oDT">源DataTable</param>
/// <returns></returns>
public static DataTable DtSelectTop(int TopItem, DataTable oDT)
{
    if (oDT.Rows.Count < TopItem) return oDT;  

    DataTable NewTable = oDT.Clone();
    DataRow[] rows = oDT.Select("1=1");
    for (int i = 0; i < TopItem; i++)
    {
        NewTable.ImportRow((DataRow)rows[i]);
    }
    return NewTable;
}
#endregion  

#region 获取DataTable中指定列的数据
/// <summary>
/// 获取DataTable中指定列的数据
/// </summary>
/// <param name="dt">数据源</param>
/// <param name="tableName">新的DataTable的名词</param>
/// <param name="strColumns">指定的列名集合</param>
/// <returns>返回新的DataTable</returns>
public static DataTable GetTableColumn(DataTable dt, string tableName, params string[] strColumns)
{
    DataTable dtn = new DataTable();
    if (dt == null)
    {
        throw new ArgumentNullException("参数dt不能为null");
    }
    try
    {
        dtn = dt.DefaultView.ToTable(tableName, true, strColumns);
    }
    catch (Exception e)
    {
        throw new Exception(e.Message);
    }
    return dtn;
}
#endregion