RDLC Report Viewer: Calculate SUM in expression in VB.Net

Dear Sir,

I'm Trying to make calculations in expression for value in Report Viewer/Rdlc in vb.net but Result do not match in VB.NET

I use an expression like this:

=SUM(Fields!UnitPrice.Value * Fields!Quantity.Value - Fields!Discount.Value)-(Parameters!pDiscountTotal.Value+Parameters!pReturTotal.Value)

Is there anything wrong with the code ?

Please Guide me

    Public Class Order
        Public Property CustomerName As String
        Public Property DiscountTotal As Integer
        Public Property ReturTotal As Integer
        Public Property OrderDetails As List(Of OrderDetail)
    End Class
    Public Class OrderDetail
        Public Property ProductName As String
        Public Property UnitPrice As Integer
        Public Property Quantity As Integer
        Public Property Discount As Integer
    End Class
    Public Class OrderBusiness
        Public Shared Function GetOrder() As Order
            Return New Order() With {
                .CustomerName = "John Doe",
                .DiscountTotal = 100,
                .ReturTotal = 200,
                .OrderDetails = New List(Of OrderDetail)() From {
                    New OrderDetail() With {
                        .ProductName = "Foo",
                        .UnitPrice = 100,
                        .Quantity = 1,
                        .Discount = 0
                    },
                    New OrderDetail() With {
                        .ProductName = "Bar",
                        .UnitPrice = 200,
                        .Quantity = 2,
                        .Discount = 50
                    },
                    New OrderDetail() With {
                        .ProductName = "Baz",
                        .UnitPrice = 50,
                        .Quantity = 3,
                        .Discount = 0
                    }
                }
            }
        End Function
    End Class
    Partial Public Class Form1
        Inherits Form

        Public Sub New()
            InitializeComponent()
        End Sub

        Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
            Dim order = OrderBusiness.GetOrder()
            Me.OrderBindingSource.DataSource = order
            Me.OrderDetailBindingSource.DataSource = order.OrderDetails
            Dim p() As Microsoft.Reporting.WinForms.ReportParameter = {
                New Microsoft.Reporting.WinForms.ReportParameter("pCustomerName", order.CustomerName.ToString()),
                New Microsoft.Reporting.WinForms.ReportParameter("pDiscountTotal", order.DiscountTotal.ToString()),
                New Microsoft.Reporting.WinForms.ReportParameter("pReturTotal", order.ReturTotal.ToString())
            }
            Me.reportViewer1.LocalReport.SetParameters(p)
            Me.reportViewer1.RefreshReport()
        End Sub
    End Class

result from code

Link image result code in report viewer

Desired result

sum(Price*Quantity-Discount)-(DiscountTotal+ReturTotal)

=600-(100+200) 

TOTAL NET : 300

Thanks