speed of Export to Excel

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C#

Hi I use the following code for export data to excel in Silverlight 5 web application, it works but speed of exporting is terrible, I want to have exporting time less than 5 sec for 4000 rows count, How can I improve it?
Thanks

public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Name2 { get; set; }
        public string Name3 { get; set; }
        public string Name4 { get; set; }
    }
    public class ProductList : ObservableCollection<Product>
    {
        public ProductList()
        {
            for (int i = 1; i < 40000; i++)
                Add(new Product() { Name = "A", Name2 = "B", Name3 = "C", Name4 = "E", Id = i });
        }

    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        dynamic excelApp;

        excelApp = AutomationFactory.CreateObject("Excel.Application");


        dynamic workbook = excelApp.workbooks;
        workbook.Add();

        dynamic sheet = excelApp.ActiveSheet;

        dynamic cell = null;
        int index = 1;

        foreach (Product emp in grid.ItemsSource)
        {
            cell = sheet.Cells[index, 1];
            cell.Value = emp.Name;

            cell = sheet.Cells[index, 2];
            cell.Value = emp.Name2;

            cell = sheet.Cells[index, 3];
            cell.Value = emp.Name3;

            cell = sheet.Cells[index, 4];
            cell.Value = emp.Name4;

            cell = sheet.Cells[index, 5];
            cell.Value = emp.Id;

            index++;
        } excelApp.Visible = true;
    }