Get Logged In User details in WPF Application using C#

Hello all,

I have a login method to check if a user is a member in my DB. My login method is only a bool and I am wondering how can I grab that current users data so I can pass it to the next window. I am checking textboxes to see if the text is valid.

One way I know I could solve this is to change my login method so it returns a user then I would have that specific user but I would like to see if I could grab the user data by checking if the data is in the DB.

Here is what I have:

        //Login XAML window.
        private void BtnLoginUser_Click(object sender, RoutedEventArgs e){
            if (string.IsNullOrEmpty(txtUsername.Text)) {
                //verify and enter username.
                MessageBox.Show("Enter your username.", "Empty", MessageBoxButton.OK, MessageBoxImage.Information);                txtUsername.Focus();
                return;
            }
            else if (string.IsNullOrEmpty(txtPassword.Password)) {
                MessageBox.Show("Enter your password.", "Empty", MessageBoxButton.OK, MessageBoxImage.Information);                txtPassword.Focus();
                return;
            }
            else {
                try {
                    if(SQLuserAccess.UserLogin(txtUsername.Text, txtPassword.Password)){

                    }
                }
            }
        }

        //SQL login method
        public static bool UserLogin(string username, string password) {
            bool valid = false;
            //SQL Login Query.
            string SQLloginQuery = "SELECT * FROM Users WHERE Username=@username AND Password=@password";
            SqlCommand cmdLogin = new SqlCommand(SQLloginQuery, connection);
            cmdLogin.Parameters.AddWithValue("@username", username);
            cmdLogin.Parameters.AddWithValue("@password", password);
            try {
                connection.Open();
                int result = (int)cmdLogin.ExecuteScalar();
                if (result > 0) {
                    valid = true;
                    MessageBox.Show("Login success");
                }
                else   MessageBox.Show("Login Failed");
            }
            catch (Exception ex) {
                ex.Message.ToString();
                throw ex;
            }
            finally{
                connection.Close();
            }
            return valid;
        }

        //This is a method I use to get the user
        public static User GetUserById(int userId{            
            string SQLreadQuery = "SELECT Username, Password, IsAdmin, UserCreatedDate " +
                                  "FROM Users WHERE UserId = " + userId; //or SELECT ea column or *.
            SqlCommand cmdRead = new SqlCommand(SQLreadQuery, connection);
            try{
                connection.Open();
                SqlDataReader reader = cmdRead.ExecuteReader(CommandBehavior.SingleRow);
                if(reader.Read()){
                    User user = new User();
                    user.UserID = Convert.ToInt32(reader["UserId"]);
                    user.Username = reader["Username"].ToString();
                    user.Password = reader["Password"].ToString();
                    user.IsAdmin = Convert.ToBoolean(reader["IsAdmin"]);
                    user.UserCreatedDate = Convert.ToDateTime(reader["UserCreatedDate"]);
                    return user;
                }
                else{
                    return null;
                }
            }
            catch(Exception ex){
                ex.Message.ToString();
                return null;
            }
            finally{
                connection.Close();
            }
        }