database now defined as singleton

Database.cs

@@ -7,8 +7,9 @@ namespace it_projekt
 {
     class Database
     {
+        private static Database _database;
         public List<Person> Persons { get; set; }
-        public Database(String username, String password)
+        private Database(String username, String password)
         {
             string connectionString = "server=localhost;port=3306;database=stammdaten;User Id=" + username + ";Password=" + password + ";";
             MySqlConnection connection = new MySqlConnection(connectionString);
@@ -36,5 +37,14 @@ namespace it_projekt
             connection.Close();
             Console.WriteLine("Done.");
         }
+
+        public static Database getDatabase(string username, string password)
+        {
+            if (_database == null)
+            {
+                _database = new Database(username, password);
+            }
+            return _database;
+        }
     }
 }