Combo Box Challenge Does Anyone know the answer

[gotham]

Has anyone got a good example of loading a data reader into a combo box. I don't want to to just load the data but also have the Id field in there as well. I can do this with a dataset, but the perfomance is very slow. I can't find any examples of doing this a datareader. Also in Vb6 you could also make performance even faster by outputing the recordset into a .dat file and loading it into the combo box from there. Has anyone got any good examples of this. I looked extensively on both these subjects and can find nothing. Help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[gotham]

Surely someone must know this. If I had posted a thread entitled VB.net is crap I going back to VB6 I would of had 20 replies By now..........

[Edneeis]

There are a few different ways of doing this, but mainly the same method as the dataset should work with the datareader. You can also make your own datarow class and inherit the other one to override the tostring method and add that. You could make a custom class with the info you want and add that to the combo. If you switch around the method you use for the dataset it should look something like this:

Dim dr As SqlClient.SqlDataReader = cmd.ExecuteReader()
        Combo1.Items.Clear()
 
        Do While dr.Read()
            Combo1.Items.Add(New PtDiagnosisItem(dr.Item("PtDxID"), dr.Item("ICD9"), dr.Item("Description")))
        Loop
        dr.Close()
        dr = Nothing
        cmd.Dispose()

[gotham]

Sorry I did not make myself clear on this. I want the id to be hidden but the description to be shown, after creating a dataset I would use the following code to do this

With CmbEquipment
.DataSource = MydataSet
.DisplayMember = "Equipment"
.ValueMember = "EquipmentId"
End With

How do I get the same but with a datareader?

[Edneeis]

Do you mean you want to bind a control to a datareader?

You can't the datareader is a forward only, read only reccordset design. You can fill it from the datareader but you can't bind to it, besides databind sucks for reasons like this.

[gotham]

the combo box will be used to update a table through an update statement but the table holds the value not the description. So I want to update the value back to the database. The user though will need to see only the description as the Id is meaningless to him

[Edneeis]

So why is it that you want to use a datareader? You can't update with a datareader. In fact you can't even move backwards in a datareader. You should be able to use a dataset just fine.

[gotham]

the issue as I mentioned is speed the dataset is slower than a datareader. The form as such is then painfully slow to run at runtime. I just want to be able to populate the combo box with a description and hide the ID.

You could do this in VB6 with a forwardly only cursor then update the database with an update sql statement. Is it seriously the case that this cannot be done in VB.net. if it is, then VB.net is a big step backwards.

[Edneeis]

You can populate with a datareader but you can't use the datasource property to do it, that is just for databinding.

Actually I guess you canuse the datasource property for more than just standard databinding, you can even bind to classes. So with that then I'm not sure if you can bind directly to the datareader, but if not then you can fill a genericlist class and use it.

Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'make data to fill list
        Dim MyList As New ArrayList()
        MyList.Add(New GenericList("Jack Hammer", 1))
        MyList.Add(New GenericList("Sledge Hammer", 2))
        MyList.Add(New GenericList("Screwdriver", 3))
        MyList.Add(New GenericList("Wrench", 4))
 
        'bind list
        ComboBox1.DataSource = MyList
        ComboBox1.DisplayMember = "Display"
        ComboBox1.ValueMember = "ID"
    End Sub
 
End Class
 
Public Class GenericList
 
    Private _Display As String
    Private _ID As Integer
 
    Public Property Display() As String
        Get
            Return _Display
        End Get
        Set(ByVal Value As String)
            _Display = Value
        End Set
    End Property
 
    Public Property ID() As Integer
        Get
            Return _ID
        End Get
        Set(ByVal Value As Integer)
            _ID = Value
        End Set
    End Property
 
    Public Sub New()
        MyBase.new()
    End Sub
 
    Public Sub New(ByVal display As String, ByVal id As Integer)
        Me.Display = display
        Me.ID = id
    End Sub
 
End Class

Or to fill the class from the datareader:

Dim dr As New Data.SqlClient.SqlDataReader(cmd)
        Dim MyList As New ArrayList()
        Do While dr.read
            MyList.Add(New GenericList(dr.Item("Equipment"), dr.Item("EquipmentID"))
        Loop
 
        'bind list
        ComboBox1.DataSource = MyList
        ComboBox1.DisplayMember = "Display"
        ComboBox1.ValueMember = "ID"
    End Sub