Question

Currently now i’m using silverlight5 with MVVM. in SL5 i need to do the following.
I have 3 textbox and 1 button control and i datagrid in the xaml(Design page).

here is the Design View(Xaml):

<UserControl.DataContext>
        <VC:EmployeeListViewModel />
    </UserControl.DataContext>
        <Grid x:Name="LayoutRoot">
        <my:DataGrid x:Name="McDataGrid" ItemsSource="{Binding Employees,UpdateSourceTrigger=PropertyChanged}" Margin="130,151,0,0" Height="137" VerticalAlignment="Top" RowBackground="#AA5D9324" AutoGenerateColumns="True" HorizontalAlignment="Left" Width="193">
        </my:DataGrid>
        <Button Content="Show Message" Width="100" Height="25" Margin="256,75,0,0" VerticalAlignment="Top" HorizontalAlignment="Left">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="Click">
                    <si:CallDataMethod Method="AddEmployeeCommand"/>
                    <si:ShowMessageBox Caption="Thank you"
                                       Message="Thanks for trying the Example"
                                       MessageBoxButton="OK"/>
                    <si:SetProperty TargetName="LayoutRoot" 
            PropertyName="Background" Value="PaleGoldenrod"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </Button>
     <TextBlock FontWeight="Bold" Height="26" HorizontalAlignment="Left" Margin="47,12,0,0" Name="textBlock1" Text="First Name:" VerticalAlignment="Top" Width="77" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="130,12,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" Text="{Binding Path=Employee.Fname}" />
        <TextBlock FontWeight="Bold" Height="25" HorizontalAlignment="Left" Margin="35,44,0,0" Name="textBlock2" Text="Second Name:" VerticalAlignment="Top" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="130,44,0,0" Name="textBox2" VerticalAlignment="Top" Width="120" />
        <TextBlock FontWeight="Bold" Height="23" HorizontalAlignment="Left" Margin="45,75,0,0" Name="textBlock3" Text="Department:" VerticalAlignment="Top" />
        <TextBox Height="23" HorizontalAlignment="Left" Margin="130,75,0,0" Name="textBox3" VerticalAlignment="Top" Width="120" />
        <!-- Add reference to Microsoft.Expression.Interactions.dll, System.Windows.Interactivity.dll -->
            <!-- Use mvvmxmlns snippet to add i and ei namespace prefixes -->
       </ComboBox> 
        <TextBlock Height="23" HorizontalAlignment="Left" Margin="64,122,0,0" Name="textBlock4" Text="Choose:" VerticalAlignment="Top" FontWeight="Bold" />
</Grid>
</UserControl>

in the same project i create one folder named ‘ViewModel’:
in the same folder i add one class file named: EmployeeListViewModel.cs

my question is this. how to pass the textbox value to the viewmodel[EmployeeListViewModel] and insert the it to the Datagrid.

EmployeeListViewModel.cs:

public class EmployeeListViewModel:INotifyPropertyChanged 
    {
        public ObservableCollection<Employee> Employees { get; private set; }

        public EmployeeListViewModel()
        {
            Employees = Silverlight_MVVM.DataHelper.EmployeeDataHelper.EmployeeData ();
        }

        private Employee _SelectedEmployee;
        public Employee SelectedEmployee
        {
            get
            {
                return _SelectedEmployee;
            }
            set
            {
                _SelectedEmployee = value;
                RaisePropertyChanged("SelectedEmployee");
            }
        }

        private Employee _Names;
        public Employee Names
        {
            get
            {
                return _Names;
            }
            set
            {
                _Names = value;
                RaisePropertyChanged("Names");
            }
        }

        public void HandleShowMessage()
        {
           // MessageBox.Show("Hello " + Names + ",Welcome to EventTrigger for MVVM.");

        }
        public RelayCommand _AddEmployeeCommand;
        /// <summary>
        /// Returns a command that show the customer.
        /// </summary>
        public ICommand AddEmployeeCommand
        {
            get
            {
                if (_AddEmployeeCommand == null)
                {
                    _AddEmployeeCommand = new RelayCommand(
                        param => this.AddEmployee(),
                        param => this.CanAddEmployee
                        );
                }
                return _AddEmployeeCommand;
            }
        }

        public bool CanAddEmployee
        {
            get
            {
                 return true;
            }
        }

        public void AddEmployee()
        {
            //Employee newEmployee = new Employee("New1);
            Employee newEmployee = new Employee() **{};**
           --> **Here i have to pass the value.. How is it possible..?**
            Employees.Add(newEmployee);
            SelectedEmployee = newEmployee;
        }



        #region INotifyPropertyChanged
        // [field: NonSerialized]
        public event PropertyChangedEventHandler PropertyChanged;

        protected void RaisePropertyChanged(string propertyName)
        {
            var handler = PropertyChanged;
            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #endregion
}

Answer 1

Not 100% sure how you are going about this?
Usually I would have the grid bound to the selected employee as you have, then have the values of the text boxes bound to the properties on the selectedemployee. As you change row, these would then update to reflect the values of the currently selected row in the grid.
So then you add a new blank employee and it would have blank values until they were entered in the text box. Of course, you’d need to build in some validation to ensure you don’t get loads of blabnk rows added.

If I’m correct in my understanding of how you are wanting to do it, then as it stands the values in the text boxes are not related to the selected row, but are used just to add a new employee with those values? to achieve this I would suggest having the Textbox bind to a string value on the Viewmodel. Currently you have them bound to something that doesn’t appear to actually exist. Instead, I’d bind them to their own properties on the view model thus:

private string _employeeFirstName; 
    public string EmployeeFirstName 
    { 
        get 
        { 
            return _employeeFirstName; 
        } 
        set 
        { 
            _employeeFirstName= value; 
            RaisePropertyChanged("EmployeeFirstName"); 
        } 
    } 

and then in the xaml bind to that property – with Mode=TwoWay so that the viewmodel also recieves any updates

<TextBox Height="23" HorizontalAlignment="Left" Margin="130,12,0,0" Name="textBox1" VerticalAlignment="Top" Width="120" Text="{Binding Path=EmployeeFirstName, Mode=TwoWay}" />

then when creating your new employee:

    public void AddEmployee()    
    {     
        Employee newEmployee = new Employee() {FName = this.EmployeeFirstName};    

        Employees.Add(newEmployee);    
        SelectedEmployee = newEmployee;    
    }