database now defined as singleton

Form1.cs

@@ -15,6 +15,7 @@ namespace it_projekt
         public Form1()
         {
             InitializeComponent();
+            this.exportBtn.Enabled = false;
         }
 
 
@@ -29,19 +30,23 @@ 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!");
             }
-            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);
+            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);
+                }
             }
         }