如何在更新方法后清除文本框

我有3个文本框、一个复选框、列表视图和3个按钮。现在，文本框和复选框已绑定到ManageUsersViewModel中的属性"User"。ListView已将其选定项绑定到属性"SelectedUser"。按钮命名为"添加"、"编辑"、"保存"。每个按钮都绑定到自己的命令。"添加"按钮的命令运行良好。当我点击它时，我从WCF服务中调用一个方法，该方法将新用户插入数据库。当我在列表视图中选择某一行，然后单击"编辑"复选框按钮，文本框就会填充我选择的值。现在我可以通过点击按钮"保存"来更改值并保存更改。问题是，在这个过程之后，我不能再添加新用户。当我尝试添加新用户时，我在文本框中输入的值也会更改我之前更改的值。基本上，我不能再做添加功能，在更新功能之后，直到我重新启动窗口。此外，我希望我的文本框和复选框在添加或更新功能后被清除。这是我的代码：

管理用户视图模型

class ManageUsersViewModel : ViewModelBase
{
   #region Constructor
    private ServiceReference1.tblUser user;
    public ServiceReference1.tblUser User    
    {
        get
        {
            return user;
        }
        set
        {
            user = value;
            OnPropertyChanged("User");
        }
    }
    private ServiceReference1.tblUser selectedUser;
    public ServiceReference1.tblUser SelectedUser
    {
        get
        {
            return selectedUser;
        }
        set
        {
            selectedUser = value;
            OnPropertyChanged("SelectedUser");
        }
    }

    private ObservableCollection<ServiceReference1.tblUser> users;
    public ObservableCollection<ServiceReference1.tblUser> Users     // Property "Service"
    {
        get
        {
            return users;
        }
        set
        {
            users = value;
            OnPropertyChanged("Users");
        }
    }
    public ManageUsersViewModel()
    {
    }   // Konstruktor
    #endregion
    public ICommand _addUser;
    public ICommand addUser 
    {
        get
        {
            if (_addUser == null)
            {
                _addUser = new DelegateCommand(delegate()
                {
                    try
                    {                            
                        Service1Client wcf = new Service1Client();
                        wcf.AddUser(User);
                        Users.Add(User);
                        wcf.Close();
                    }
                    catch
                    {
                        Trace.WriteLine("working...", "MyApp");
                    }
                });
            }
            return _addUser;
        }
    }
 public ICommand _btnEditUser;
    public ICommand btnEditUser
    {
        get
        {
            if (_btnEditUser == null)
            {
                _btnEditUser = new DelegateCommand(delegate()
                {
                    try
                    {
                        User = SelectedUser;
                    }
                    catch
                    {
                        Trace.WriteLine("working...", "MyApp");
                    }
                });
            }
            return _btnEditUser;
        }
    }
    public ICommand _btnUpdateUser;
    public ICommand btnUpdateUser
    {
        get
        {
            if (_btnUpdateUser == null)
            {
                _btnUpdateUser = new DelegateCommand(delegate()
                {
                    try
                    {
                        Service1Client wcf = new Service1Client();
                        wcf.updateUser(SelectedUser);
                        wcf.Close();                           

                    }
                    catch
                    {
                        Trace.WriteLine("working...", "MyApp");
                    }
                });
            }
            return _btnUpdateUser;
        }
    }
}

管理用户.xaml

<TextBox Height="25" HorizontalAlignment="Left" Margin="124,12,0,0" Name="txtName" VerticalAlignment="Top" Width="156" BorderBrush="#89000000" FontFamily="Times New Roman" FontSize="14" TabIndex="0" Text="{Binding Path=User.Name}" />
    <TextBox Height="25" HorizontalAlignment="Left" Margin="124,43,0,0" Name="txtNewUsername" VerticalAlignment="Top" Width="156" BorderBrush="#89000000" FontFamily="Times New Roman" FontSize="14" TabIndex="1" Text="{Binding Path=User.Username}" />
    <TextBox Height="25" HorizontalAlignment="Left" Margin="124,74,0,0" Name="txtPassword" VerticalAlignment="Top" Width="156" BorderBrush="#89000000" FontFamily="Times New Roman" FontSize="14" TabIndex="2" Text="{Binding Path=User.Password}" />
    <Button Content="Dodaj" Height="23" HorizontalAlignment="Left" Margin="286,12,0,0" Name="btnAddUser" VerticalAlignment="Top" Width="73" BorderBrush="Black" FontFamily="Times New Roman" FontWeight="Bold" FontSize="15" IsDefault="True" Command="{Binding addUser}" />
    <Button Content="Izmeni" Height="23" HorizontalAlignment="Left" Margin="381,152,0,0" Name="btnEditUser" VerticalAlignment="Top" Width="73" BorderBrush="Black" FontFamily="Times New Roman" FontWeight="Bold" FontSize="15" Command="{Binding btnEditUser}" />
    <Button BorderBrush="Black" Content="Sačuvaj" FontFamily="Times New Roman" FontSize="15" FontWeight="Bold" Height="23" HorizontalAlignment="Left" IsDefault="True" Margin="361,12,0,0" Name="btnUpdateUser" VerticalAlignment="Top" Width="73" Visibility="Visible" Command="{Binding btnUpdateUser}"/>
    <CheckBox Content="Administrator" Height="16" HorizontalAlignment="Left" Margin="124,110,0,0" Name="checkBox1" VerticalAlignment="Top" BorderBrush="#89000000" FontFamily="Times New Roman" FontWeight="Bold" FontSize="14" TabIndex="3" IsChecked="{Binding User.IsAdmin}" />
    <ListView SelectionMode="Single" Height="204" HorizontalAlignment="Left" Margin="7,152,0,0" Name="lvUsers" VerticalAlignment="Top" Width="368" FontFamily="Times New Roman" FontSize="14" ItemsSource="{Binding Path=Users}" FontWeight="Bold" Foreground="Black" BorderBrush="Black" SelectedItem="{Binding Path=SelectedUser}">

public ICommand addUser 
{
    get
    {
        if (_addUser == null)
        {
            _addUser = new DelegateCommand(delegate()
            {
                try
                {                            
                    Service1Client wcf = new Service1Client();
                    wcf.AddUser(User);
                    Users.Add(User);
                    wcf.Close();
                    this.User = new User();
                }
                catch
                {
                    Trace.WriteLine("working...", "MyApp");
                }
            });
        }
        return _addUser;
    }
}

User=new ClSUser();