DropDownList.Da taSource = Nothing ???

[Marc Robitaille]

Hello,

I set the DataSource property of a DropDownList to as DataSet that is filled
from a SQLDataAdapter. The AutoPostBack property of that DropDownList is set
to True. When the SelectedIndexCh anged occurs, if I set a BreakPoint in the
event and I check the values in the Watch window, I can see that the
DataSource property still contain the DataSet. When I set the DataSource of
a DropDownList to my object collection and check the values in the Watch
window when the SelectedIndexCh anged occurs, the DataSource is set to
Nothing. Why? What appen to my object? Is my object need something so that
the DataSource property of the DropDownList can retain my object collection?
Hope that someone can help me.

Here are some parts of my code of my object collection. I have a VTBCodes
class that is a collection. I allso have VTBCode class that represent the
data. VTBCodes inherits from PAICollectionBa se and implements iEntitys.
PAICollectionBa se inherits from CollectionBase of the .net framework.
VTBCode inherits from EntityBase. EntityBase implements iEntity.

<Serializable() > Public MustInherit Class PAICollectionBa se
Inherits CollectionBase
Implements IDisposable

Public MustOverride Function Add(ByVal pObject As Object) As Integer

.....

End Class

Public Interface iEntitys

Function GetData() As iEntitys
....

End Try

<Serializable() > Public Class VTBCodes
Inherits PAICollectionBa se
Implements iEntitys

Public Overrides Function Add(ByVal pEntity As Object) As Integer
If TypeOf (pEntity) Is VTBCode Then
....
Else
Dim ex As New Exception("...
Throw ex
End If
....

Public Overloads Function GetData() As PAIiFactory.iEn titys Implements
PAIiFactory.iEn titys.GetData
Dim oconConnection As System.Data.Sql Client.SqlConne ction
Dim odrVTBCode As System.Data.Sql Client.SqlDataR eader = Nothing

oconConnection = Me.GetConnectio n

Dim strSQL As String = "Select...

odrVTBCode = SqlHelper.Execu teReader(oconCo nnection, CommandType.Tex t,
strSQL)

While odrVTBCode.Read
oVTBCode = New VTBCode

oVTBCode.Desc.V alue =
odrVTBCode.Item (oVTBCode.Desc. AliasName(False ))

list.Add(oVTBCo de)

End While

Return Me
....

End Class

Public Interface iEntity

Sub UpdateData(ByVa l pConnection As
System.Data.Sql Client.SqlConne ction, ByVal pTrans As
System.Data.Sql Client.SqlTrans action)

Sub DeleteData(ByVa l pConnection As
System.Data.Sql Client.SqlConne ction, ByVal pTrans As
System.Data.Sql Client.SqlTrans action)

Sub InsertData(ByVa l pConnection As
System.Data.Sql Client.SqlConne ction, ByVal pTrans As
System.Data.Sql Client.SqlTrans action)
....

End Interface

Public MustInherit Class EntityBase
Implements iEntity
Implements IDisposable

Public MustOverride Function GetData(ByVal pExpressionColl ection As
iExpression) As iEntity Implements PAIiFactory.iEn tity.GetData

Public MustOverride Overloads Sub UpdateData(ByVa l pConnection As
System.Data.Sql Client.SqlConne ction, ByVal pTrans As
System.Data.Sql Client.SqlTrans action) Implements
PAIiFactory.iEn tity.UpdateData

Public MustOverride Overloads Sub DeleteData(ByVa l pConnection As
System.Data.Sql Client.SqlConne ction, ByVal pTrans As
System.Data.Sql Client.SqlTrans action) Implements
PAIiFactory.iEn tity.DeleteData

Public MustOverride Overloads Sub InsertData(ByVa l pConnection As
System.Data.Sql Client.SqlConne ction, ByVal pTrans As
System.Data.Sql Client.SqlTrans action) Implements
PAIiFactory.iEn tity.InsertData

....

End Class

<Serializable() > Public Class VTBCode
Inherits EntityBase

Private mfldDescFr As FieldString
....

Public Sub New()

mfldDesc = New FieldString("De sc", Me, "Desc", 100)'Name , Me,
AlisaName, Length
...

End Sub
....
Public Property Desc() As FieldString
Get
Return mfldDesc

End Get
Set(ByVal Value As FieldString)
mfldDesc = Value

End Set

End Property
....

Public Overrides Function GetData(ByVal pExpressionColl ection As
iExpression) As iEntity
....

Public Overrides Function ToString() As String

'This will show the value in the DropDownList
Return Convert.ToStrin g(mfldDesc.Valu e)

End Function
....

End Class

This is the code to fill the DropDownList

Dim oVTBCodes As New VTBCodes

cboCodeDivision .DataSource = oVTBCodes.GetDa ta
cboCodeDivision .DataBind()

[zdrakec]

"cboCodeDivisio n.DataSource = oVTBCodes.GetDa ta
cboCodeDivision .DataBind() "

Be sure to set the DataText and DataValue properties of your drop-down:

cboCodeDivision .DataTextField = "FieldName"
cboCodeDivision .DataValueField = "FieldName"

Also, when the page reloads, its datasource will be nothing; so try
storing the dataset in the page cache if you need to retrieve it later:

Cache.Insert("k eynamefordatase t",dataset)

You can get it back:
dataset = ctype(Cache.Ite m("keynameforda taset"),dataset )

(I use "dataset" here for, really, any object).

Even though the datasource of your dropdown goes to Nothing, the text
and value properties you set at databinding time will still be
available:

cboCodeDivision .SelectedItem.T ext and
cboCodeDivision .SelectedItem.V alue

Hope this is helpful....
zdrakec

[Marc Robitaille]

Thank you. It help me :-)
Bye

"zdrakec" <zd*****@yahoo. com> a écrit dans le message de news:
11************* ********@g47g20 00...legro ups.com...

"cboCodeDivisio n.DataSource = oVTBCodes.GetDa ta
cboCodeDivision .DataBind() "

Be sure to set the DataText and DataValue properties of your drop-down:

cboCodeDivision .DataTextField = "FieldName"
cboCodeDivision .DataValueField = "FieldName"

Also, when the page reloads, its datasource will be nothing; so try
storing the dataset in the page cache if you need to retrieve it later:

Cache.Insert("k eynamefordatase t",dataset)

You can get it back:
dataset = ctype(Cache.Ite m("keynameforda taset"),dataset )

(I use "dataset" here for, really, any object).

Even though the datasource of your dropdown goes to Nothing, the text
and value properties you set at databinding time will still be
available:

cboCodeDivision .SelectedItem.T ext and
cboCodeDivision .SelectedItem.V alue

Hope this is helpful....
zdrakec