Connect Directly To Aspnetdb Database?

I wanna connect to aspnetdb but it makes an error says "Login failed for user" this is the connection string in web config :

<add name="UserProfiles" connectionString="Data Source=KIA;Initial Catalog=aspnetdb;Integrated Security=True;"
providerName="System.Data.SqlClient" />

and this is my code:

SqlConnection connection = new SqlConnection();
SqlCommand ComNewCheckSum = new SqlCommand();
connection.ConnectionString = ConfigurationManager.ConnectionStrings["UserProfiles"].ConnectionString;
connection.Open();
ComNewCheckSum.Connection = connection;
ComNewCheckSum.CommandText = String.Format("select UserID from aspnet_Users where UserName = {0}", _UserName);
return Convert.ToInt32(ComNewCheckSum.ExecuteScalar());

how can i pass through error?