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sreenath
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Joined:
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College: ESEC
Degree: M.Sc
Department: CSE
State: TN
Fav Quote: no pain no gain
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Sat Oct 03, 2009 3:02 pm
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Post subject: Serializing a ListView to XML 
Why should I migrate to .NET? Another reason is Serialization (saving objects to files) to XML is so simple in NET.
In this article, I will show you how easy it is to save the contents of a ListView to an XML file and then reload the ListView from XML.
Three VB.NET methods are used in this article. The first method is SaveObjectProperties. In this application, I have a ListView with twenty-two columns in it. I have a need to save the contents of the ListView and the next time I run the application, I want to populate the ListView with the data that was loaded in it the last time the application was run. SaveObjectProperties will do that for me. First, I create a new DataTable, named "PrintObject", in a DataSet. Next, I loop to add twenty-two columns to the DataTable. They are simply named "Col0" to "Col21". There names do not really matter as you will see in the reload method. Next, I loop thru the the ListView, creating an object for each row of the ListView and then calling AddRowToTable to add each object to the DataTable. Finally, I call the WriteXML method of the DataSet object. It does the creation of the XML automatically.
Public Sub SaveObjectProperties()
Dim ds As New DataSet
Dim oCG As New CGrid
Dim i As Integer
Try
' create a datatable in a dataset. the dataset will
' automatically create the xml
Dim dt As DataTable = ds.Tables.Add("PrintObject")
For i = 0 To MelistviewObjects.Columns.Count - 1
dt.Columns.Add("Col" & i.ToString, Type.GetType("System.String"))
Next
For i = 0 To MelistviewObjects.Items.Count - 1
With Me.listviewObjects.Items(i)
Dim o() As Object = {.SubItems(0).Text, _
.SubItems(1).Text, _
.SubItems(2).Text, _
.SubItems(3).Text, _
.SubItems(4).Text, _
.SubItems(5).Text, _
.SubItems(6).Text, _
.SubItems(7).Text, _
.SubItems(8).Text, _
.SubItems(9).Text, _
.SubItems(10).Text, _
.SubItems(11).Text, _
.SubItems(12).Text, _
.SubItems(13).Text, _
.SubItems(14).Text, _
.SubItems(15).Text, _
.SubItems(16).Text, _
.SubItems(17).Text, _
.SubItems(18).Text, _
.SubItems(19).Text, _
.SubItems(20).Text, _
.SubItems(21).Text}
AddRowToTable(dt, o)
End With
Next i
ds.WriteXml(Me.textSavePath.Text)
Catch ex As System.Exception
MsgBox(ex.ToString)
End Try
End Sub
This method simply adds an object array to the passed DataTable. Note that we can build a DataTable in memory, that is not linked to a database. That is one of the neat things about ADO.NET.
Public Function AddRowToTable(ByRef dt As DataTable, _
ByVal ParamArray DRows() As Object) As Boolean
Dim i As Short
Try
Dim newRow As DataRow = dt.NewRow
For i = 0 To UBound(DRows)
' add a row to the passed dtList
newRow(i) = DRows(i)
Next
dt.Rows.Add(newRow)
Return True
Catch ex As System.Exception
MsgBox(ex.ToString)
Return False
End Try
End Function
This method reloads the ListView from the previously created XML file. First, I create a new DataSet object and use it to read the XML file. As you can see, ADO.NET and XML work seamlessly. Next, I get a DataTable object set to the "PrintObject" DataTable saved as XML. Finally, I loop through each row and column of the DataTable to fill the ListView. ADO.NET, XML, and VB.NET make formerly complex tasks become a cakewalk!
Public Sub ReloadListviewFromXML()
Dim ds As New DataSet
Try
ds.ReadXml(Me.textOpenPath.Text)
Dim dt As DataTable = ds.Tables("PrintObject")
Dim i As Integer
Dim j As Integer
Me.listviewObjects.Items.Clear()
For i = 0 To dt.Rows.Count - 1
Dim dr As DataRow = dt.Rows(i)
With Me.listviewObjects
.Items.Add(dr(0))
For j = 1 To dt.Columns.Count - 1
.Items(i).SubItems.Add(dr(j))
Next
End With
Next
Catch ex As System.Exception
StructuredErrorHandler(ex)
End Try
End Sub
_________________
sreenath@myanna.in
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