How to call the datatable fill code without double in vb.net - vb.net

Question

How to call the datatable fill code without double in vb.net?.
in the code below you might see I wrote back the fill datatable code if there is a solution without me writing it back in "GenerateReport()". Please Recommend.
Thanks
Private WithEvents dt As New DataTable
Public Sub fillDataGridView1()
dt = New DataTable
Dim query As String = "SELECT NOD,ITM,CIA,DPR,QTY FROM RSD WHERE QTY > 0 AND PNM=#PNM"
Using con As OleDbConnection = New OleDbConnection(GetConnectionString)
Using cmd As OleDbCommand = New OleDbCommand(query, con)
cmd.Parameters.AddWithValue("#PNM", ComboBox1.SelectedValue)
Using da As New OleDbDataAdapter(cmd)
da.Fill(dt)
da.Dispose()
Dim totalColumn As New DataColumn()
totalColumn.DataType = System.Type.GetType("System.Double")
totalColumn.ColumnName = "Total"
totalColumn.Expression = "[CIA]*[QTY]*(1-[DPR]/100)"
dt.Columns.Add(totalColumn)
Me.grid.DataSource = dt
Me.grid.Refresh()
End Using
End Using
End Using
End Sub
Private Sub GenerateReport()
KtReport1.Clear()
'the code below actually already exists but I reuse it
dt = New DataTable
Dim query As String = "SELECT NOD,ITM,CIA,DPR,QTY FROM RSD WHERE QTY > 0 AND PNM=#PNM"
Using con As OleDbConnection = New OleDbConnection(GetConnectionString)
Using cmd As OleDbCommand = New OleDbCommand(query, con)
cmd.Parameters.AddWithValue("#PNM", ComboBox1.SelectedValue)
Using da As New OleDbDataAdapter(cmd)
da.Fill(dt)
Dim dtCloned As DataTable = dt.Clone()
dtCloned.Columns("CIA").DataType = GetType(String)
For Each row As DataRow In dt.Rows
dtCloned.ImportRow(row)
Next row
KtReport1.AddDataTable(dtCloned)

Answer 1

The issue is that you are essentially duplicating code despite the fact that you have a variable setup to hold the filled DataTable at the Form level.
What I would suggest doing is creating a function that returns the filled DataTable, then at the top of your two existing methods do a null check against the Form level variable.
Take a look at this example:
Private _dt As DataTable
Private Function GetAndFillDataTable() As DataTable
Dim dt As New DataTable()
Dim query As String = "SELECT NOD,ITM,CIA,DPR,QTY FROM RSD WHERE QTY > 0 AND PNM=#PNM"
Using con As OleDbConnection = New OleDbConnection(GetConnectionString)
Using cmd As OleDbCommand = New OleDbCommand(query, con)
cmd.Parameters.AddWithValue("#PNM", ComboBox1.SelectedValue)
Using da As New OleDbDataAdapter(cmd)
da.Fill(dt)
da.Dispose()
Dim totalColumn As New DataColumn()
totalColumn.DataType = System.Type.GetType("System.Double")
totalColumn.ColumnName = "Total"
totalColumn.Expression = "[CIA]*[QTY]*(1-[DPR]/100)"
dt.Columns.Add(totalColumn)
Return dt
End Using
End Using
End Using
End Function
Private Sub FillDataGridView1()
If (_dt Is Nothing) Then
_dt = GetAndFillDataTable()
End If
grid.DataSource = _dt
grid.Refresh()
End Sub
Private Sub GenerateReport()
If (_dt Is Nothing) Then
_dt = GetAndFillDataTable()
End If
Dim dtCloned As DataTable = _dt.Clone()
dtCloned.Columns("CIA").DataType = GetType(String)
For Each row In _dt.Rows
dtCloned.ImportRow(row)
Next row
KtReport1.AddDataTable(dtCloned)
End Sub