问unity3d sqlite错误为命令提供的参数不足

EN

public void login(){
    var sql_login = "SELECT username,password FROM my_users WHERE username = @login_username AND password = @login_password;";
    SqliteCommand createCommand = new SqliteCommand (sql_login, dbCon);
    using (var cmd =  dbCon.CreateCommand()) {
        cmd.CommandText = sql_login;
        cmd.Parameters.AddWithValue("@login_username",login_username.text);
        cmd.Parameters.AddWithValue("@login_password",login_password.text);
        cmd.ExecuteNonQuery();

        SqliteDataReader dr = createCommand.ExecuteReader();
        int count = 0;

        while(dr.Read()){
            count++;
        }

        if(count == 1){
            Application.LoadLevel("Succes");
        }

        if(count > 1){
            print("Duplicate");
        }

        if(count < 1){
            print("Not Found");
        }

    }
}