Combobox not being filled after introduction of login form - vb.net

Question

I have the following code in my UC_Menu_Scout class:
Private Sub cmbScoutName_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbScoutName.SelectedIndexChanged
If loaded = True Then
cmbReportDate.DataSource = Nothing
cmbReportDate.DataSource = frmPlayerInfo.filterReports()
cmbReportDate.DisplayMember = "ReportDate"
cmbReportDate.ValueMember = "ReportID"
End If
End Sub
Private Sub cmbReportDate_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbReportDate.SelectedIndexChanged
If loaded = True Then
If cmbReportDate.Items.Count > 0 Then
'frmPlayerInfo.myDataTable = Nothing
frmPlayerInfo.myDataTable = frmPlayerInfo.retrieveDT()
dgPlayers.DataSource = frmPlayerInfo.myDataTable
frmPlayerInfo.setReport()
End If
End If
End Sub
And the following code in my frmPlayerInfo class (just the relevant code):
Public myDataTable As DataTable = Nothing
Private Sub frmPlayerInfo_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
UC_Menu_Scout1.cmbScoutName.DataSource = retrieveScouts()
UC_Menu_Scout1.cmbScoutName.DisplayMember = "ScoutName"
UC_Menu_Scout1.cmbScoutName.ValueMember = "ScoutID"
UC_Menu_Scout1.cmbReportDate.DataSource = filterReports()
UC_Menu_Scout1.cmbReportDate.DisplayMember = "ReportDate"
UC_Menu_Scout1.cmbReportDate.ValueMember = "ReportID"
myDataTable = retrieveDT()
UC_Menu_Scout1.dgPlayers.DataSource = myDataTable
setReport()
loaded = True
End Sub
Public Function retrieveDT() As DataTable
Dim Str As String = _
<String> SELECT
Player.PlayerID,
PlayerFirstName,
PlayerLastName,
DOB,
Age,
PlaceOfBirth,
PlayerImage
FROM
Player
INNER JOIN
Report ON Report.PlayerID = Player.PlayerID
/*WHERE
ReportID = #ReportID*/
ORDER BY
PlayerFirstName
</String>
Dim dt As New DataTable
Using conn As New SqlClient.SqlConnection(DBConnection)
conn.Open()
Using cmdQuery As New SqlClient.SqlCommand(Str, conn)
cmdQuery.Parameters.Add("#ReportID", SqlDbType.Int).Value = UC_Menu_Scout1.cmbReportDate.SelectedItem.ReportID
cmdQuery.CommandTimeout = 600
Try
Using daResults As New SqlClient.SqlDataAdapter(cmdQuery)
daResults.Fill(dt)
End Using
Catch ex As Exception
MsgBox("An Exception has happened: " & ex.Message & vbNewLine)
End Try
End Using 'Automatically closes connection
End Using
Return dt
End Function
Everything worked fine before I created a login form. Since then (upon a successful login) I've been receiving the "Object variable or with block variable not set" error on my comboboxes- saying they were now empty at the time of the form load event. Since setting the "loaded" boolean, this got rid of the error for frmPlayerInfo.filterReports(), however I still receive the same message for frmPlayerInfo.retrieveDT- on this line cmdQuery.Parameters.Add("#ReportID", SqlDbType.Int).Value = UC_Menu_Scout1.cmbReportDate.SelectedItem.ReportID. Again, saying the combobox (cmbReportDate) is empty.
The intial load event works, but the crash occurs on the cmbReportDate_SelectedIndexChanged event, on this line: frmPlayerInfo.myDataTable = frmPlayerInfo.retrieveDT() in the retrieveDT function.
If I remove the login form I have no such problems- any answers specific to my program would be appreciated.

Answer 1

Here's an example of how to get a reference to the main Form from within your UserControl:
Dim frm As Form = Me.FindForm
If TypeOf frm Is frmPlayerInfo Then
Dim player As frmPlayerInfo = DirectCast(frm, frmPlayerInfo)
' ... now do something with "player" ...
End If
No, this is not a good design because now your UserControl can only ever be used with the frmPlayerInfo Form. If you're okay with that, then here's an example using your specific code:
Private Sub cmbReportDate_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbReportDate.SelectedIndexChanged
If loaded = True Then
If cmbReportDate.Items.Count > 0 Then
Dim frm As Form = Me.FindForm
If TypeOf frm Is frmPlayerInfo Then
Dim player As frmPlayerInfo = DirectCast(frm, frmPlayerInfo)
' ... now do something with "player" ...
player.myDataTable = player.retrieveDT()
dgPlayers.DataSource = player.myDataTable
player.setReport()
End If
End If
End If
End Sub