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dnarayan
Joined: 22 Oct 2007
Posts: 3
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 Posted: Mon Oct 22, 2007 1:25 pm Post subject: Sorting DatabaseBrowser |
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I am by no means an expert programmer but I have been tasked with making a viewer for a database of sorts. The database is actually just a bunch of CSV files which I can open as a database using ADO. I have been able to populate the tree and define multiple levels and what not. However, I can not figure out how to make it sort correctly.
I think it has something to do with the TypedListName and TypeName properties in the databinding tab. In the DatabaseBrowser sample the different classes (Vehicle, Incident) are placed in the TypedListName whereas in mine I can only get the thing to work properly if I put them in TypeName. The structures of my classes are identical to the example (with different names) and they inherit VirtualRecord. Am I missing something?
Example class I am using:
| Code: |
Imports System
Imports Infralution.VirtualData
Public Class dbScript
Inherits VirtualRecord
Public ReadOnly Property ID() As Long
Get
Return CLng(GetValue("ID"))
End Get
End Property
Public ReadOnly Property fType() As String
Get
Return IIf(CStr(GetValue("fType")) = "Date", "RunDate", CStr(GetValue("fType")))
End Get
End Property
Public ReadOnly Property Name() As String
Get
Dim alpha As String
alpha = GetValue("mName")
If Double.TryParse(alpha, Nothing) Then
If CLng(alpha) > 30000 Then
alpha = Format(Date.FromOADate(CDbl(alpha)), "d MMMM yyyy")
End If
End If
Return CStr(alpha)
End Get
End Property
Public ReadOnly Property Runs() As RunRecordset
Get
If _runs Is Nothing Then
_runs = New RunRecordset(fType, GetValue("mName"))
End If
Return _runs
End Get
End Property
Private _runs As RunRecordset
End Class
Public Class ScriptRecordset
Inherits VirtualRecordset
Dim fType As String
Public Sub New(ByVal filterType As String)
MyBase.New(GetType(dbScript), LogDatabase.Connection, "Runs", "ID", "SELECT DISTINCT " & IIf(filterType = "Date", "RunDate", filterType) & " AS mName, 1 AS ID, '" & filterType & "' AS fType FROM runs.csv runs LEFT JOIN structure.csv structure ON runs.ScriptID = structure.ID")
Me.Refresh(True)
fType = filterType
Me.SortDirection = ComponentModel.ListSortDirection.Ascending
If fType = "Date" Then
Me.SortDirection = ComponentModel.ListSortDirection.Descending
End If
End Sub
Protected Overrides Function GetSortClause() As String
Select Case SortField
Case Nothing
Return IIf(fType = "Date", "RunDate", fType) & " {0}"
Case Else
Return MyBase.GetSortClause()
End Select
End Function
End Class |
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Infralution
Joined: 28 Feb 2005
Posts: 5027
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| Posted: Mon Oct 22, 2007 10:43 pm Post subject: |
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You are right - it is related to using the TypedListName. If you specify this it indicates to Virtual Tree that the datasource supports the ITypedList interface. Virtual Tree can then use the methods provided by this interface to implement sorting.
For a VirtualRecordset the TypedListName is the name of the table that the recordset is bound to. So in your case you would need to specify "Runs" as the TypedListName (I'm guessing that is the name of the table). In the sample project we use a convention of naming the strongly typed VirtualRecord the same as the table - so this distinction isn't so obvious.
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Infralution Support |
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dnarayan
Joined: 22 Oct 2007
Posts: 3
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| Posted: Tue Oct 23, 2007 8:59 am Post subject: |
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Thanks so much that fixed the problem.
Now I have another question: when I sort, it queries child records that have not been expanded yet for some reason. This also occurs in the databasebrowser sample. I have a very large database and these queries make sorting VERY slow. Is there some way to prevent the queries to the children if they are not expanded? |
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Infralution
Joined: 28 Feb 2005
Posts: 5027
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| Posted: Tue Oct 23, 2007 10:03 pm Post subject: |
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The child record queries occur because Virtual Tree needs to determine whether each of the displayed rows has children (to determine whether the expansion indicator should be displayed). You can change this behaviour by setting the RowBinding.ChildPolicy to LoadOnExpand. This means that the expansion indicator is always displayed initially and the query is only performed if the user expands a row. A side effect of this is that if a row does not have any children then when the user expands the row the expansion indicator will disappear.
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Infralution Support |
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