Adding a 'Choose One' item to combo box

Adding a 'Choose One' item to combo box

Old forum URL: forums.lhotka.net/forums/t/4144.aspx

JonM posted on Thursday, January 10, 2008

In a search window I have a read-only collection of possible types to be used as a paramter in my search.  However, I want to add an extra item to the combo like 'Choose One'.  If set to 'Choose One' it would actually be null and I would know not to use this parameter in the search.  So far the only way I've found to achieve this is to muck up my read only collection in order to get it to add an extra.  Any ideas on this one?  It seems to me like it would be a common thing you would want to do.

JoeFallon1 replied on Thursday, January 10, 2008

This has been discussed many times. There are some interesting solutions posted too. You should be able to find them with a Search.

As I recall there is one very nice solution which abstracts this whole idea nd lets you add whatever the phrase of the day is - "Choose One", "blank", "Add New", "Pick anything but me", etc.

I usually have 2 methods on my NVL which tell me to retrieve the data or add the "fake first row" and then then retrieve the data.

Joe

 

mr_lasseter replied on Thursday, January 10, 2008

Look about half way down for the HeaderedBindingList.

http://forums.lhotka.net/forums/2/4613/ShowThread.aspx

 

mike

JohnB replied on Thursday, January 10, 2008

Here is one method of doing it.

Let's assume that we wish to fill a combo with customers so I would have the following:

<Serializable()> _
Public Class CustomerComboList
    Inherits Csla.ReadOnlyListBase(Of CustomerComboList, CustomerComboInfo)

    Public Shared Function GetCustomerComboList(Optional ByVal FirstItemInList As String = "") As CustomerComboList

        Return Csla.DataPortal.Fetch(Of CustomerComboList)(New Criteria(FirstItemInList))

    End Function

In my Criteria object for the CustomerComboList I would have the following:

Private Class Criteria

    Private _firstItemInList As String = String.Empty

    Public ReadOnly Property FirstItemInList() As String
        Get
            Return _firstItemInList
        End Get
    End Property

    Public Sub New(ByVal FirstItemInList As String)
        _firstItemInList = FirstItemInList
    End Sub

End Class

Finally the Fetch:

  Private Sub Fetch(ByVal criteria As Criteria)

      RaiseListChangedEvents = False

      Using cn As New SqlConnection(MyConfig.DataConnection)
          cn.Open()
          Using cm As SqlCommand = cn.CreateCommand
              With cm
                  .CommandType = CommandType.StoredProcedure
                  .CommandText = "SomeProcName"
                  Using dr As New Csla.Data.SafeDataReader(.ExecuteReader)
                      IsReadOnly = False

                      '-- Check to see if we need to add a custom first item to the list
                      If criteria.FirstItemInList.Length > 0 Then
                          Dim firstItem As CustomerComboInfo = New LocationInfo(-1, criteria.FirstItemInList)
                          Me.Add(firstItem)
                      End If

                      While dr.Read()
                          Dim info As New CustomerComboInfo(dr.GetInt32(0), dr.GetString(1), dr.GetInt32(2))
                          Me.Add(info)
                      End While
                      IsReadOnly = True
                  End Using
              End With
          End Using
      End Using

      RaiseListChangedEvents = True

  End Sub

End Class

I used -1 to distinguish the new entry but you could use whatever you want here.

I'm sure there are many ways of doing this but hopefully it helps you out!

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