Using one dataset in many forms - vb.net

Question

I am using vb.net to load data from sql server database. I have defined a dataset in my module
and want to use it in many forms Public dsDataset As DataSet. When I load the main form I load the options that are likely to be the same in all the forms like the departments and sections, so that I do not have to load them again in all the forms. When Navigating from main form to an other form I pass this dataset in a the form constructor.
In the main form I am loading these options:
Sub loadOptions()
Dim da As SqlDataAdapter
Dim sql As String
Try
sqlConn = New SqlConnection(connString)
sqlConn.Open()
sql = " select depId, name from DEPARTMENT "
da = New SqlDataAdapter(sql, sqlConn)
da.Fill(dsDataset, "department")
sql = " select select depId, sectionId, name from SECTION "
da = New SqlDataAdapter(sql, sqlConn)
da.Fill(dsDataset, "section")
'----------------------------------------------------------------------
sqlConn.Close()
Catch ex As Exception
sqlConn.Close()
MsgBox(Err.Description)
End Try
End Sub
Then lets say I have printers form where I load data from from the database and use the option in the dsDataset instead of loading them again. I pass the dataset as follows:
Dim printers As frmPrinters = New frmPrinters(dsDataset)
printers.ShowDialog()
and in the printers form I have a constructor as follows:
Sub New(ByRef dsDataset As DataSet)
InitializeComponent()
cmbDepartment.DataSource = dsDataset.Tables("department")
cmbDepartment.DisplayMember = "name"
cmbDepartment.ValueMember = "depId"
cmbSection.DataSource = dsDataset.Tables("section")
cmbSection.DisplayMember = "name"
cmbSection.ValueMember = "sectionId"
End Sub
and load all the printers to the dataset with no problem:
sql = "select * from printer where printerId=" & printerId
daPrinter = New SqlDataAdapter(sql, sqlConn)
daPrinter.Fill(dsDataset, "printer")
dgvPrinters.DataSource = dsDataset.Tables("printers")
Now when I double click any of the printers I go an other form to load the details of that particular printer as follows:
printerId = dgvPrinters.Rows(dgvPrinters.CurrentRow.Index).Cells(0).Value
printerMode = "modify"
Dim printer As New frmPrinter(dsDataset)
printer.ShowDialog()
In the new form I use the same constructor above but the problem happens there. The following error comes:
Value cannot be null.
Parameter name: dataSet
What I am doing wrong?

Answer 1

It doesn't look like you are saving the dsDataset anywhere in your constructor. For example in a private variable. My guess is that inside frmPrinters you will have a public dsDataSet variable which you never set to anything.
So what you should do is the following:
Create a private dsDataSet variable in frmPrinter called _dsDataset:
Private _dsDataset As DataSet
In the constructor do this:
_dsDataset = dsDataset
And finally in the doubleclick event send the private variable:
Dim printer As New frmPrinter(_dsDataset)
And then you should be fine.