MVVM and Silverlight help

I am trying to learn the MVVM pattern using Silverlight. There are tons of videos 开发者_开发知识库and blogs. I understand it in a high level, but cant seem to get my own implementation of it.

I got the following View:

<UserControl x:Class="SilverlightApplication1.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:vm="clr-namespace:SilverlightApplication1.ViewModel"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="White">
        <TextBlock Text="{Binding Name, Mode=TwoWay}" Width="200" Height="200"/>
        <Button Name="btn1" Width="200" Height="20" Margin="100,268,100,12" Click="btn1_Click"/>

    </Grid> </UserControl>

In my VM, I have: namespace SilverlightApplication1.ViewModel

{
    public class ViewModel : INotifyPropertyChanged
    {
        private Model.UserModel m_model;

        public ViewModel()
        {
            m_model = new Model.UserModel();
        }

        public string Name 
        {
            get
            {
                return m_model.Name;
            }
            set
            {
                if (value != m_model.Name)
                {
                    m_model.Name = value;
                    InvokePropertyChanged("Name");
                }
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void InvokePropertyChanged(string propertyName)
        {
            if (this.PropertyChanged != null)
            {
                this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }

        }


    }
}

and in my Model:

namespace SilverlightApplication1.Model
{
    public class UserModel
    {
        public string Name { get; set; }    
    }
}

Basically, I want to simulate a button click and update the property so that it can fire the property changed event. I tried hard coding the property on the MainPage code behind like this:

private void btn1_Click(object sender, RoutedEventArgs e)
        {
            ViewModel.ViewModel vm = new ViewModel.ViewModel();
            vm.Name = "Test";
        }

Shouldnt this update the property (for Name) and raise the propertychanged event? I have seen other examples do something similar to this. I dont understand as to what is subscribing to the event

Can anyone shine some light?

In this example, to fix it, try this code:

private void btn1_Click(object sender, RoutedEventArgs e)
        {
            ViewModel.ViewModel vm = new ViewModel.ViewModel();
            this.LayoutRoot.DataContext = vm;
            vm.Name = "Test";
        }

Note: I know you just learning MVVM, but after you're comfortable with this paradigm, you should adopt a framework so you can focus on things besides the MVVM plumbing. In saying that, doing things in the code-behind is not the MVVM way, like setting the data context. However, I assume you're just experimenting and learning, so it's fine for now.

I think the step you're missing here is setting the WPF form's datacontext to an instance of your viewmodel.In your xaml set your UserControl datacontext to a new viewmodel like below:

<UserControl.DataContext>
  <vm:ViewModel />
</UserControl.DataContext>

Then just do normal sets in your vm and it should bubble up the changes to your binding.