Object reference not set to an instance of an object. Dropdownlist

Question

I'm getting the following error:

Object reference not set to an instance of an object.

Server Error in '/WebSite3' Application.

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Here is my code

Partial Class frmChoseIncident
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles      Me.Load
    
    Dim objCDBGuest As New CDBGuestProfile
    Dim objCGuest As New CGuestProfile





    Dim arrList As New ArrayList

    If Page.IsPostBack = False Then

        Dim intGuestID1 As Integer
        intGuestID1 = Request.QueryString("id")
        objCGuest = objCDBGuest.getOneIncident(intGuestID1)

        txtIncidentName.Text = objCGuest.IncidentName
        txtIncidentSummary.Text = objCGuest.IncidentSummary
        txtRoomRate.Text = objCGuest.RoomRate
        txtArrivalDate.Text = objCGuest.ArrivalDate
        txtDepartureDate.Text = objCGuest.DepartureDate
        txtGuestName.text = objCGuest.GuestName
        txtCompany.Text = objCGuest.GuestCompany
        txtIncidentDate.Text = objCGuest.IncidentDate
        txtAddedDate.Text = objCGuest.AddedDate
        txtRoomID.Text = objCGuest.RoomId
        txtPreparedBy.Text = objCGuest.PreparedBy
        txtDepartment.Text = objCGuest.Department
        txtGuestTime.Text = objCGuest.GuestTime

        lstHotel.SelectedItem.Value = objCGuest.Hotel
        txtAction.Text = objCGuest.Action
        txtCost.Text = objCGuest.Cost
        txtComplimentary.Text = objCGuest.Complimentary
        txtAmount.Text = objCGuest.Amount
        lstGlitchStatus.SelectedItem.Value = objCGuest.GlitchStatus
        lstGuestHistory.SelectedItem.Value = objCGuest.GuestHistory
        txtComments.Text = objCGuest.Comments


        lstHotel.SelectedItem.Enabled = False
        txtAction.ReadOnly = True
        txtCost.ReadOnly = True
        txtComplimentary.ReadOnly = True
        txtAmount.ReadOnly = True
        lstGlitchStatus.SelectedItem.Enabled = False
        lstGuestHistory.SelectedItem.Enabled = False
        txtComments.ReadOnly = True



        txtIncidentName.ReadOnly = True
        txtIncidentSummary.ReadOnly = True
        txtRoomRate.ReadOnly = True
        txtArrivalDate.ReadOnly = True
        txtDepartureDate.ReadOnly = True
        txtGuestName.ReadOnly = True
        txtCompany.ReadOnly = True
        txtIncidentDate.ReadOnly = True
        txtRoomID.ReadOnly = True
        txtPreparedBy.ReadOnly = True
        txtDepartment.ReadOnly = True
        txtGuestTime.ReadOnly = True
    End If

End Sub

The Function

 Public Function getOneIncident(ByVal pintGuestID1 As Integer) As CGuestProfile
    Dim objCmd As New MySqlCommand
    Dim objCn As New MySqlConnection(connectionString)
    Dim objAdapter As New MySqlDataAdapter
    Dim strSQL As String = ""
    Dim objDs As New DataSet
    Dim objDataRow As DataRow

    strSQL = "SELECT * FROM tblGuestProfile WHERE strGuestCodeTI=" & pintGuestID1
    objCmd.CommandText = strSQL
    objCmd.Connection = objCn
    objAdapter.SelectCommand = objCmd

    objCn.Open()

    objAdapter.Fill(objDs, "tblGuestProfile")
    objDataRow = objDs.Tables("tblGuestProfile").Rows(0)
    Dim objCGuestProfile As New CGuestProfile

    objCGuestProfile.GuestName = objDataRow.Item("strGuestNameTI")
    objCGuestProfile.GuestCompany = objDataRow.Item("strGuestCompanyTI")
    objCGuestProfile.ArrivalDate = objDataRow.Item("strArrivalDateTI")
    objCGuestProfile.DepartureDate = objDataRow.Item("strDepartureDateTI")
    objCGuestProfile.IncidentDate = objDataRow.Item("strIncidentDateTI")
    objCGuestProfile.AddedDate = objDataRow.Item("strAddedDateTI")
    objCGuestProfile.RoomRate = objDataRow.Item("strRoomRateTI")
    objCGuestProfile.RoomId = objDataRow.Item("intRoomTI")
    objCGuestProfile.PreparedBy = objDataRow.Item("strPreparedByTI")
    objCGuestProfile.Department = objDataRow.Item("strDepartmentTI")
    objCGuestProfile.GuestTime = objDataRow.Item("strTimeTI")
    objCGuestProfile.IncidentName = objDataRow.Item("strIncidentNameTI")
    objCGuestProfile.IncidentSummary = objDataRow.Item("strIncidentSummaryTI")

    objCGuestProfile.Hotel = objDataRow.Item("intHotelTI")
    objCGuestProfile.Action = objDataRow.Item("strActionTI")
    objCGuestProfile.Cost = objDataRow.Item("strCostTI")
    objCGuestProfile.Complimentary = objDataRow.Item("strComplimentaryTI")
    objCGuestProfile.Amount = objDataRow.Item("strAmountTI")
    objCGuestProfile.GlitchStatus = objDataRow.Item("intGlitchStatusTI")
    objCGuestProfile.GuestHistory = objDataRow.Item("intGuestHistoryTI")
    objCGuestProfile.Comments = objDataRow.Item("strCommentsTI")
    objCn.Close()
    Return objCGuestProfile
End Function

The CGuestProfile

Imports Microsoft.VisualBasic

Public Class CGuestProfile
Private strGuestCodeTI As String
Private strGuestNameTI As String
Private strGuestCompanyTI As String
Private strArrivalDateTI As String
Private strDepartureDateTI As String
Private strIncidentDateTI As String
Private strAddedDateTI As String
Private intRoomTI As String
Private strRoomRateTI As String
Private strPreparedByTI As String
Private strDepartmentTI As String
Private strTimeTI As String
Private strIncidentNameTI As String
Private strIncidentSummaryTI As String
Private intHotelTI As Integer
Private intGuestHistoryTI As Integer
Private strComplimentaryTI As String
Private intGlitchStatusTI As Integer
Private strActionTI As String
Private strCostTI As String
Private strAmountTI As String
Private strCommentsTI As String


Public Property GuestId() As String
    Get
        Return strGuestCodeTI
    End Get
    Set(ByVal value As String)
        strGuestCodeTI = value
    End Set
End Property

Public Property GuestName() As String
    Get
        Return strGuestNameTI
    End Get
    Set(ByVal value As String)
        strGuestNameTI = value
    End Set
End Property

Public Property GuestCompany() As String
    Get
        Return strGuestCompanyTI
    End Get
    Set(ByVal value As String)
        strGuestCompanyTI = value
    End Set
End Property

Public Property ArrivalDate() As String
    Get
        Return strArrivalDateTI
    End Get
    Set(ByVal value As String)
        strArrivalDateTI = value
    End Set
End Property

Public Property DepartureDate() As String
    Get
        Return strDepartureDateTI
    End Get
    Set(ByVal value As String)
        strDepartureDateTI = value
    End Set
End Property

Public Property IncidentDate() As String
    Get
        Return strIncidentDateTI
    End Get
    Set(ByVal value As String)
        strIncidentDateTI = value
    End Set
End Property
Public Property AddedDate() As String
    Get
        Return strAddedDateTI
    End Get
    Set(ByVal value As String)
        strAddedDateTI = value
    End Set
End Property

Public Property RoomId() As Integer
    Get
        Return intRoomTI
    End Get
    Set(ByVal value As Integer)
        intRoomTI = value
    End Set
End Property

Public Property RoomRate() As String
    Get
        Return strRoomRateTI
    End Get
    Set(ByVal value As String)
        strRoomRateTI = value
    End Set
End Property

Public Property PreparedBy() As String
    Get
        Return strPreparedByTI
    End Get
    Set(ByVal value As String)
        strPreparedByTI = value
    End Set
End Property

Public Property Department() As String
    Get
        Return strDepartmentTI
    End Get
    Set(ByVal value As String)
        strDepartmentTI = value
    End Set
End Property

Public Property GuestTime() As String
    Get
        Return strTimeTI
    End Get
    Set(ByVal value As String)
        strTimeTI = value
    End Set
End Property
Public Property IncidentName() As String
    Get
        Return strIncidentNameTI
    End Get
    Set(ByVal value As String)
        strIncidentNameTI = value
    End Set
End Property
Public Property IncidentSummary() As String
    Get
        Return strIncidentSummaryTI
    End Get
    Set(ByVal value As String)
        strIncidentSummaryTI = value
    End Set
End Property
Public Property Hotel() As Integer
    Get
        Return intHotelTI
    End Get
    Set(ByVal value As Integer)
        intHotelTI = value
    End Set
End Property

Public Property Action() As String
    Get
        Return strActionTI
    End Get
    Set(ByVal value As String)
        strActionTI = value
    End Set
End Property

Public Property Cost() As String
    Get
        Return strCostTI
    End Get
    Set(ByVal value As String)
        strCostTI = value
    End Set
End Property
Public Property Complimentary() As String
    Get
        Return strComplimentaryTI
    End Get
    Set(ByVal value As String)
        strComplimentaryTI = value
    End Set
End Property

Public Property Amount() As String
    Get
        Return strAmountTI
    End Get
    Set(ByVal value As String)
        strAmountTI = value
    End Set
End Property
Public Property GlitchStatus() As Integer
    Get
        Return intGlitchStatusTI
    End Get
    Set(ByVal value As Integer)
        intGlitchStatusTI = value
    End Set
End Property

Public Property GuestHistory() As Integer
    Get
        Return intGuestHistoryTI
    End Get
    Set(ByVal value As Integer)
        intGuestHistoryTI = value
    End Set
End Property
Public Property Comments() As String
    Get
        Return strCommentsTI
    End Get
    Set(ByVal value As String)
        strCommentsTI = value
    End Set
End Property
End Class

If i take away the

lstHotel.SelectedItem.Value = objCGuest.Hotel
lstGlitchStatus.SelectedItem.Value = objCGuest.GlitchStatus
lstGuestHistory.SelectedItem.Value = objCGuest.GuestHistory
lstHotel.SelectedItem.Enabled = False
lstGlitchStatus.SelectedItem.Enabled = False
lstGuestHistory.SelectedItem.Enabled = False

Then i can load the page, however the dropdownlist is empty.

Hotel function

Public Function getAllHotelDropDownList() As ArrayList
    Dim objCn As New MySqlConnection(connectionString)
    Dim objCmd As New MySqlCommand
    Dim objAd As New MySqlDataAdapter

    Dim objDs As New DataSet
    Dim objDr As DataRow

    Dim strSQL As String = "SELECT * FROM tblHotel"

    Dim objArrayList As New ArrayList
    Dim objHotel As New CHotel

    objCmd.Connection = objCn
    objAd.SelectCommand = objCmd
    objCmd.CommandText = strSQL
    objCn.Open()
    objAd.Fill(objDs, "tblHotelData")

    For Each objDr In objDs.Tables("tblHotelData").Rows
        objHotel = New CHotel
        objHotel.Hotel = objDr.Item("intHotelHO")
        objHotel.strHotel = objDr.Item("strHotelHO")
        objArrayList.Add(objHotel)
    Next
    Return objArrayList

End Function
Public Function getOneHotel(ByVal pstrHotelTI As Integer) As CHotel
    Dim objCmd As New MySqlCommand
    Dim objCn As New MySqlConnection(connectionString)
    Dim objAdapter As New MySqlDataAdapter
    Dim strSQL As String = ""
    Dim objDs As New DataSet
    Dim objDataRow As DataRow

    strSQL = "SELECT * FROM tblHotel WHERE intHotelHO=" & pstrHotelTI
    objCmd.CommandText = strSQL
    objCmd.Connection = objCn
    objAdapter.SelectCommand = objCmd

    objCn.Open()

    objAdapter.Fill(objDs, "tblHotel")
    objDataRow = objDs.Tables("tblHotel").Rows(0)
    Dim objCHotel As New CHotel

    objCHotel.strHotel = objDataRow.Item("strHotelHO")
    
    objCn.Close()
    Return objCHotel
End Function
End Class

Answer 1

I am not 100% sure what you are trying to do with the ddlist, but if I understand it, you want to update the value of the list to be the current information.

If this is the case, then you should not be altering the SelectedItem, you should be setting the SelectedValue:

lstHotel.SelectedValue = objCGuest.Hotel
lstGlitchStatus.SelectedValue = objCGuest.GlitchStatus
lstGuestHistory.SelectedValue = objCGuest.GuestHistory

Likewise, if you are trying to disable the list rather than the item in the list, then you need:

lstHotel.Enabled = False
lstGlitchStatus.Enabled = False
lstGuestHistory.Enabled = False

You might want to look through the MSDN documentation for SelectedItem and its data type ListItem.

If it turns out that you do want to work directly with a SelectedItem, you will have to test it for existence first and, if needed, select an item in the list or add one.

If lstHotel.SelectedItem Is Nothing Then
   ' Nothing in the list, so add it
   If lstHotel.Items.Count = 0 Then
       lstHotel.Items.Add(New ListItem)
   End If
   ' Select the first item in the list
    lstHotel.SelectedIndex = 0
End If
lstHotel.SelectedItem.Value = objCGuest.Hotel
lstHotel.SelectedItem.Enabled = False