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;
+        }
     }
 }

Form1.cs

@@ -15,6 +15,7 @@ namespace it_projekt
         public Form1()
         {
             InitializeComponent();
+            this.exportBtn.Enabled = false;
         }
 
 
@@ -29,21 +30,25 @@ namespace it_projekt
         private void loginBtn_Click(object sender, EventArgs e)
         {
             LoadUsersFromTable(this.userTxt.Text, this.passTxt.Text);
+
         }
 
 
 
         public void LoadUsersFromTable(string user, string password)
         {
-            if (db == null)
+            db = Database.getDatabase(user, password);
+            if (db.Persons == null)
             {
-                db = new Database(user, password);
+                MessageBox.Show("Connection to Database failed! \nPlease Try again.", "Database Error!");
             }
+            else {
                 foreach (Person person in db.Persons)
                 {
                     this.dataGrid.Rows.Add(person.Id, person.Firstname, person.Lastname, person.department_short, person.department_long, person.CreationDate, false);
                 }
             }
+        }
 
         private void dataGrid_CellContentClick(object sender, DataGridViewCellEventArgs e)
         {