Problem restoring database

Question

Hello,
I have a database Application and i want to create Backup nad restore Utility in the .Net Application.
for that I am Using the ,

using Microsoft.SqlServer.Management.Smo;
using Microsoft.SqlServer.Management.Common;


backup Process is Working fine but restore cannot work..
Code to restore the database is as Follows

  private void btnrestore_Click(object sender, EventArgs e)
        {
            string result = string.Empty;
            try
            {
               
                OpenFileDialog ofd = new OpenFileDialog();
                if (srv != null)
                {
                    ofd.Title = "Restore BackUp...";
                    ofd.Filter = "Backup File|*.bak";
                    if (ofd.ShowDialog() == DialogResult.OK)
                    {
                        Restore re_db = new Restore();
                        re_db.Action = RestoreActionType.Database;
                        re_db.Database = clsDatabase.DatabaseName;
                        BackupDeviceItem bk_item = new BackupDeviceItem(ofd.FileName, DeviceType.File);
                        re_db.Devices.Add(bk_item);
                        re_db.ReplaceDatabase = true;
                        re_db.SqlRestore(srv);

                        MessageBox.Show(this, "The Restore of Database "+clsDatabase.DatabaseName+" Completed Successfully!!.", "Workmate.NET", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    }
                }
                else
                {
                    MessageBox.Show("A connection to a SQL server was not established.", "Not Connected to Server", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                }
            }
            catch (FailedOperationException exfa)
            {
                result = "FailedOperationException error in Backup " + exfa.Message + Environment.NewLine;
                result += "  Operation : " + exfa.Operation + Environment.NewLine;
                result += "  TargetSite : " + exfa.TargetSite + Environment.NewLine;
                result += "  StackTrace : " + exfa.StackTrace + Environment.NewLine;
                MessageBox.Show(result);
            }
            catch (SmoException exsmo)
            {
                result = "Smo error in Backup " + exsmo.Message + Environment.NewLine;
                result += " SmoExceptionType " + Enum.GetName(typeof(SmoExceptionType), exsmo.SmoExceptionType) + Environment.NewLine;
                result += " TargetSite : " + exsmo.TargetSite + Environment.NewLine;
                result += " StackTrace : " + exsmo.StackTrace + Environment.NewLine;
                if (exsmo.InnerException != null)
                {
                    result += "  Inner 1 : " + exsmo.InnerException.Message + Environment.NewLine;
                }
                MessageBox.Show(result);
            }
            catch (Exception exgen)
            {
                result = "Generic error in Backup " + exgen.Message + Environment.NewLine;
                if (exgen.InnerException != null)
                {
                    result += " Inner 1 : " + exgen.InnerException.Message + Environment.NewLine;
                    if (exgen.InnerException.InnerException != null)
                    {
                        result += "  Inner 2 : " + exgen.InnerException.InnerException.Message + Environment.NewLine;
                    }
                    // i needed only one time to go further in the innerexception in 4 years
                    MessageBox.Show(result);
                }
            }
        }

when i run this code it gives an error saying 'FailedOperationException error in Backup Restore failed for Server'


can anybody have any idea  !!!