complete login function and login window also add attached properties and helper classes for securestring

Server Dashboard/ViewModels/LoginViewModel.cs

@@ -1,15 +1,62 @@
 using System;
 using System.Collections.Generic;
+using System.Security;
 using System.Text;
+using System.Windows.Input;
 
 namespace Server_Dashboard {
-    class LoginViewModel {
-        private string password;
+    class LoginViewModel : BaseViewModel {
 
-        public string Password {
-            get { return password; }
-            set { password = value; }
+        private string username;
+
+        public string Username {
+            get { return username; }
+            set {
+                if (username != value)
+                    username = value;
+                OnPropertyChanged(nameof(username));
+            }
         }
 
+        private string errorText;
+
+        public string ErrorText {
+            get { return errorText; }
+            set {
+                if (errorText != value)
+                    errorText = value;
+                OnPropertyChanged(nameof(errorText));
+            }
+        }
+
+
+        public LoginViewModel() {
+            LoginCommand = new RelayCommand(Login);
+        }
+
+        public ICommand LoginCommand { get; set; }
+
+        private void Login(object parameter) {
+            if (!String.IsNullOrWhiteSpace(Username) && !String.IsNullOrWhiteSpace((parameter as IHavePassword).SecurePassword.Unsecure())) {
+                if (DatabaseHandler.CheckLogin(Username, (parameter as IHavePassword).SecurePassword.Unsecure())) {
+                    Console.WriteLine();
+                } else {
+                    ErrorText = "Username or password is wrong.";
+                    return;
+                }
+            } else if (String.IsNullOrWhiteSpace(Username) && String.IsNullOrWhiteSpace((parameter as IHavePassword).SecurePassword.Unsecure())) {
+                ErrorText = "Please provide a username and password";
+                return;
+            }
+            if (String.IsNullOrWhiteSpace(Username)) {
+                ErrorText = "Username cannot be empty.";
+                return;
+            }
+            if (String.IsNullOrWhiteSpace((parameter as IHavePassword).SecurePassword.Unsecure())) {
+                ErrorText = "Password cannot be empty.";
+                return;
+            }
+            ErrorText = "";
+        }
     }
 }