Sort a datatable

Sort a datatable

• Chin Tian

  You can try using the Select method of the DataTable class. This allows for you to sort also. To get the associated column name to sort by using the index of the column, you can use the existing DataColumnCollection exposed by the Columns property. After you call the Select method you can import the sorted array of DataRows into a new DataTable via the ImportRow method.

  Depending on how the original DataTable was created you can have the same name.

  smc750

  
  
  

• senordotnet

  This is how I accomplished the task, however I do not this the class realy needs to be used in this instance I have future use for it

  Using the click event I take the values from a listbox and sort them

  Protected Sub btnAdd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnAdd.Click

  Dim lcol As New ListItemCollection
  Dim utility As New clsUtilities
  Dim dt As New DataTable
  Dim lstItm As ListItem

  For Each lstItm In lbxUsers.Items

  If lstItm.Selected Then
  lcol.Add(lstItm)
  End If

  Next
  Dim intCounter As Int16

  dt = utility.ResetListBox(lcol)
  Dim strColumnName As String = dt.Columns(0).ColumnName
  Dim myDataView As New DataView(dt)

  myDataView.Sort = strColumnName
  For intCounter = 0 To dt.Rows.Count - 1
  lbxAcceptedUsers.Items.Add(myDataView(intCounter).Item(1))
  Next
  
  For intCounter = 0 To lcol.Count - 1

  lbxUsers.Items.Remove(lcol(intCounter))
  lbxAcceptedUsers.ClearSelection()

  Next
  
  End Sub

  this class noted above "dt = utility.ResetListBox(lcol)" I create a datatable from listbox1's values and use them
  to load the second listbox2

  Public Function ResetListBox(ByVal lcolRaw As ListItemCollection) As DataTable

  'Dim x As Int16
  Dim dt As New DataTable
  Dim dr As DataRow
  Dim itm As ListItem = Nothing

  
  With dt.Columns

  .Add("text", System.Type.GetType("System.String"))
  .Add("value", System.Type.GetType("System.String"))

  End With

  For Each itm In lcolRaw
  If itm.Text <> "" Then

  dr = dt.NewRow

  With dr

  .Item("text") = itm.Text
  .Item("value") = itm.Value

  End With

  dt.Rows.Add(dr)

  End If
  Next

  
  dt.AcceptChanges()

  
  Return dt
  End Function

  
  

• Mike Fang

  I wrote a couple of tutorials that talk about sorting a DataTable. I recommend creating a DataView from the DataTable:

  DataView Sorting Filtering and DataBinding in ADO.NET 2.0 - Converting DataView to Table - ADO.NET Tutorials

  Regards,

  Dave

  
  
  

• Douglas Chor

  Ideally if you only need to sort the data once then you should sort the data on the DB side when it is returned. However assuming that you support client-side sorting (such as column headers) then you can use the DataTable.Select() method to retrieve the desired rows and sort them at the same time. The first parameter is the filtering criteria while the second parameter is the column name(s) to sort on and the optional direction (such as "Name ASC"). The returned collection will be filtered and sorted appropriately. Note that I believe the filter can be empty to indicate all rows. Look at DataColumn.Expression for how to build this string. To get the column name from a column index use DataTable.Columns[index].ColumnName.

  Michael Taylor - 5/15/06

  
  
• Sort a datatable