Private Sub btnCompute_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCompute.Click
        'the compute function is used to evaluate an expression on a DataTable with a filter..

        'As a precautional step, to avoid errors, i am reloading the DataTable..
        'Using a Data adapter to load data into the DataTable..
        'You can refer these urls: 
        'http://www.planetsourcecode.com/vb/scripts/ShowCode.asp?txtCodeId=4790&lngWId=10 or 
        'http://www.a1vbcode.com/app-3771.asp for information to use DataAdapters..
        DA = New OleDb.OleDbDataAdapter("Select * from Employees", CN)
        DT = New DataTable
        DA.Fill(DT)

        'initializing command builder, this will be used later..
        CMB = New OleDb.OleDbCommandBuilder(DA)
    End Sub

    'This function will get an array of DataRows as argument and display them in the DataGrid..
    Sub ShowInDataGrid(ByVal ArgDRs() As DataRow)
        Dim TmpDT As New DataTable
        TmpDT = DT.Clone 'Gets the Structure of DT and assigns to TmpDT..

        For i As Integer = 0 To ArgDRs.Length - 1
            TmpDT.ImportRow(ArgDRs(i)) 'adds the DataRow arrays to the TmpDT, this ImportRow() method is explained separately..
        Next

        DataGrid1.DataSource = TmpDT

        Dim TmpVal As Double
        'here i am using the sum() function as expression and "DeptID=10" as filter to find out the sum of Salary column where DeptID=10..
        TmpVal = DT.Compute("sum(salary)", "DeptID=10")
        MsgBox("Total salary given for Department 10 is : " & TmpVal, MsgBoxStyle.Information, Me.Text)
    End Sub