DataTable方法 和 性能

列的循序调整

 

 1         Private Function AdjustFirstColumn(ByVal dsData As DataSet, ByVal firstColName As String) As DataSet
 2             Dim bl As Boolean = False
 3             For Each dt As DataTable In dsData.Tables
 4                 For Each drpt As DataColumn In dt.Columns
 5                     If drpt.ColumnName = firstColName Then
 6                         bl = True
 7                     End If
 8                 Next
 9                 If bl Then
10                     dt.Columns(firstColName).SetOrdinal(0)
11                 End If
12             Next
13             Return dsData
14 
15         End Function

 

 按一定数量行进行切割

 

 1         Private Function splitDataTable(ByVal dt As DataTable, ByVal ColNumb As Integer) As DataSet
 2 
 3             Dim leftThird As Integer = dt.Rows.Count Mod ColNumb
 4             Dim timesThird As Integer = (dt.Rows.Count - leftThird) / ColNumb    这个有4舍五入现象 所以 要减掉 这个 余数 先，再开始整除
 5 
 6             Dim ds As New DataSet()
 7 
 8             For i As Integer = 1 To timesThird
 9                 Dim dt1 As DataTable = dt.Clone()
10                 Dim j As Integer
11 
12                 For j = (i - 1) * ColNumb To (i * ColNumb - 1)
13                     dt1.Rows.Add(dt.Rows(j).ItemArray)
14                 Next
15 
16 
17 
18                 dt1.TableName = dt.TableName + i.ToString()
19                 ds.Tables.Add(dt1)
20             Next
21 
22             If leftThird > 0 Then
23                 Dim dt2 As DataTable = dt.Clone()
24                 Dim j As Integer
25 
26                 For j = timesThird * ColNumb To leftThird + timesThird * ColNumb - 1
27                     dt2.Rows.Add(dt.Rows(j).ItemArray)
28                 Next
29 
30 
31 
32                 dt2.TableName = dt.TableName + (timesThird + 1).ToString()
33                 ds.Tables.Add(dt2)
34             End If
35             Return ds
36         End Function

 

 按某列进行分组

 

 1 IEnumerable<IGrouping<string, DataRow>> result = dt.Rows.Cast<DataRow>().GroupBy<DataRow, string>(dr => dr[strGroupBy1].ToString());                    
 2    int j = 0;
 3    foreach (IGrouping<string, DataRow> ig in result)
 4   {
 5       DataTable dt1 = dt.Clone();
 6       j++;
 7       foreach (var dr_gp1 in ig){
 8             dt1.Rows.Add(dr_gp1.ItemArray);                                        
 9        }
10        dt1.TableName = dt.TableName + j.ToString();
11                                    
12        if (dt1.Rows.Count > 0)
13        {
14           dsGroup1.Tables.Add(dt1);
15        }               

 

 过滤

 

     dt.DefaultView.RowFilter = "colname=" + xxxx;
2     if (dt.DefaultView.Count > 0)
3     {
4         string str = dt.DefaultView[0]["ColumnsName"].ToString()); 
5     }