private void Form1_Load(object sender, System.EventArgs e)
{    
    System.IO.MemoryStream strm = new System.IO.MemoryStream();    
    rptMemoryStream rpt = new rptMemoryStream();    
    rpt.Run();    
    rpt.Document.Save(strm);    
    byte[] theBytes = new byte[strm.Length];    
    strm.Read(theBytes, 0, (int)strm.Length);    
    strm.Position =0;    
    viewer1.Document.Load(strm);
}

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load        
    Dim strm As New System.IO.MemoryStream()        
    Dim rpt As New rptMemoryStream()        
    rpt.Run()        
    rpt.Document.Save(strm)        
    Dim theBytes(strm.Length) As Byte        
    strm.Read(theBytes, 0, Int(strm.Length))        
    strm.Position = 0        
    Viewer1.Document.Load(strm)    
End Sub