public virtual void ShowPreview()

Public Overridable Sub ShowPreview

using DevExpress.XtraPrinting;
using DevExpress.XtraGrid.Views.Grid;
// ...

// Create printing components.
PrintingSystem printingSystem1 = new PrintingSystem();
PrintableComponentLink printableComponentLink1 = new PrintableComponentLink();
// ...

private void Form1_Load(object sender, EventArgs e) {
    // Add the link to the printing system's collection of links.
    printingSystem1.Links.AddRange(new object[] { printableComponentLink1 });

    // Assign a control to be printed by this link.
    printableComponentLink1.Component = gridControl1;

    // Assign the printing system to the document viewer.
    documentViewer1.PrintingSystem = printingSystem1;
}

Imports DevExpress.XtraPrinting
Imports DevExpress.XtraGrid.Views.Grid
' ...

' Create printing components.
Private printingSystem1 As PrintingSystem = New PrintingSystem()
Private printableComponentLink1 As PrintableComponentLink = New PrintableComponentLink()
' ...

Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) _
Handles MyBase.Load
    ' Add the link to the printing system's collection of links.
    printingSystem1.Links.AddRange(New Object() { printableComponentLink1 })

    ' Assign a control to be printed by this link.
    printableComponentLink1.Component = gridControl1

    ' Assign the printing system to the document viewer.
    documentViewer1.PrintingSystem = printingSystem1
End Sub

Lesson1 lesson = new Lesson1(printingSystem1);
    lesson.ShowPreview();
}

// Create a document and show it in the document preview.
    link.ShowPreview();
}

public void ShowPreview() {
    link.ShowPreview();
}

Dim lesson As New Lesson1(printingSystem1)
    lesson.ShowPreview()
End Sub

' Create a document and show it in the document preview.
    link.ShowPreview()
End Sub

Public Sub ShowPreview()
    Me.link.ShowPreview()
End Sub