Backup and Restore Sql Server Database With Asp.net

Hi
i Wrote Following Command In cs File (page.aspx.cs):

SqlConnection.ClearAllPools();
SqlConnection con = new SqlConnection("Data Source=(local);Initial Catalog=master;Integrated Security=True");
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandTimeout = 60;
//try
//{
cmd.CommandText = "use master";
cmd.ExecuteNonQuery();
cmd.CommandText = "ALTER DATABASE Hajir_DB SET SINGLE_USER";
cmd.ExecuteNonQuery();
cmd.CommandText = "Restore Database Hajir_DB From Disk='~\\BackUp\\" + ((String).CommandArgument) + ".dat'";
cmd.ExecuteNonQuery();
cmd.CommandText = "ALTER DATABASE Hajir_DB SET MULTI_USER";
cmd.ExecuteNonQuery();

But This Code Throw Exception:

Cannot Open Backup Device ( File-Path )

and Restore Not Complete.