Export To Excel in lightswitch 2011 for web

namespace Service {
	using System.ServiceModel.DomainServices.Hosting;
	using System.ServiceModel.DomainServices.Server;
	using System.Data.SqlClient;
	using System.Data;
	using Microsoft.Office.Interop.Excel;
	using System.Runtime.InteropServices;

	// TODO: Create methods containing your application logic.
	[EnableClientAccess()]
	public class MyDomainService: DomainService {
		public int ExportToExcel() {
			DataSet ds = new DataSet();
			using(SqlConnection connection = new SqlConnection(@"
                        your_db_connection_string;")) {
				connection.Open();
				using(SqlCommand command = new SqlCommand("Select * From Country", connection)) {
					using(SqlDataAdapter adapter = new SqlDataAdapter(command)) {
						adapter.Fill(ds);
						if (ds != null) {
							if (ds.Tables.Count > 0) {
								Application ExcelApp = new Application();
								Workbook ExcelWorkBook = null;
								Worksheet ExcelWorkSheet = null;

								ExcelApp.Visible = true;
								ExcelWorkBook = ExcelApp.Workbooks.Add(XlWBATemplate.xlWBATWorksheet);
								ExcelWorkSheet = ExcelWorkBook.Worksheets[1];

								int count = 1;
								foreach(DataRow row in ds.Tables[0].Rows) {
									ExcelWorkSheet.Cells[count, 1] = row["CountryName"].ToString();
									count++;
								}
								ExcelWorkBook.SaveAs(string.Format(@"c:\temp\{0}.xlsx", System.Guid.NewGuid()));
								ExcelWorkBook.Close();
								ExcelApp.Quit();
								Marshal.ReleaseComObject(ExcelWorkSheet);
								Marshal.ReleaseComObject(ExcelWorkBook);
								Marshal.ReleaseComObject(ExcelApp);
							}
						}
					}
				}
			}
			return 1;
		}
	}
}

partial void ExportToExcel_Execute() {
	Dispatchers.Main.BeginInvoke(() = >{

		MyDomainContext context = new MyDomainContext();
		InvokeOperation < int > invoke = context.ExportToExcel(OpCompleted, null);
	});
}
private void OpCompleted(InvokeOperation < int > invokeOp) {
	if (!invokeOp.HasError) {
		this.ShowMessageBox(invokeOp.Value.ToString());
	}
}

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