I have a visitor selection mmPicker configured to search based on Lastname.
Here are the mmPicker properties set:
PicklistValueMember = VisitorId
PicklistDisplayMember = VisitorLastName
PicklistSearchField = VisitorLastNameColumn
DataCommand = Select * From Visitors Order By VisitorLastName, VisitorFirstName, CompanyName
DataCommandType = Text

When the following code is called I get an "Input string was not in a correct format." error:

    Private Sub VisitorSelectionPicker_ItemSelected(ByVal sender As System.Object, ByVal e As OakLeaf.MM.Main.Windows.Forms.mmPickerItemSelectedEventArgs) Handles VisitorSelectionPicker.ItemSelected

        ' Find the position of the primary key selected in the Picker
        Dim visitorIdSelected As Integer = _
            CInt(e.dsSelectedItems.Tables.Item(0).Rows(0).Item("VisitorId"))

        ' TODO - Deterimine why Me.VisitorDataset assignment fails with "Input string was not in a correct format." error
        Me.VisitorDataset = _
            CType(Me.oVisitor.GetVisitorByVisitorId(visitorIdSelected), VisitorDataset)

    End Sub

The Bus Obj method is as follows (the SQL works when run in Query Analyzer):

    ' Returns a DataSet containing a Visitor for a specified VisitorId
    Public Function GetVisitorByVisitorId(ByVal visitorId As Integer) As DataSet

        ' Get a reference to the data access object
        Dim dao As mmDataAccessBase = Me.GetDataAccessObject()

        ' Create and configure parameter objects
        Dim visitorParam As IDbDataParameter = _
            dao.CreateParameter("@VisitorId", visitorId)

        ' Get a DataSet filled with the result set
        Dim dsVisitor As DataSet = _
        Me.GetDataSet( _
            "SELECT * FROM Visitors WHERE" + _
            " VisitorId = @VisitorId Order By Visitors.VisitorLastName, " _
            + "Visitors.VisitorFirstName", visitorParam)

        Return dsVisitor

    End Function

What am I missing getting this to work as desired?