MVVM: how to create a ViewModel from Model object - wpf

Question

I want to get values of my model and create a viewmode
In my Model I have
public class TestElement
{
public TestElement CurrentNode { get; set; }
public TestElement Parent { get; set; }
}
I have some method that do this
if (thisNode == null)
{
thisNode = new TestElement { Name = name, Parent = CurrentNode };
currentCollection.Add(thisNode);
}
In my view model I want to create TestElementViewModel Parent and get my model Parent values
public class TestElementViewModel
{
public TestElementViewModel Parent { get; set; }
I want to use it in this method
public IEnumerable<TestElementViewModel> ToTreeViewModel(IEnumerable<TestElement> treemodel)
{
foreach (TestElementitem in treemodel)
yield return new TestElementViewModel
{
Id = item.Id,
Name = item.Name,
Children = ToTreeViewModel(item.Children).ToList(),
Parent = item.Parent
};
}
}
How can I achieve that?

Answer 1

I'm guessing your casting error occurs on the the line
Parent = item.Parent
Well the Parent property in your TestElementViewModel isn't a TestElement type so you can't do that.
Try assigning a new TestElementViewModel instead.
Parent = new TestElementViewModel { Id = item.Parent.Id, Name = item.Parent.Name, ... }
One improvement you might want to consider is using wrappers in your ViewModel class, which will make assigning properties a little easier.
For example,
public class TestElementViewModel : INotifyPropertyChanged
{
public TestElementViewModel(TestElement model)
{
Model = model;
if(Model.Parent != null)
Parent = new TestElementViewModel(Model.Parent);
}
public TestElement Model { get; private set; }
private TestElementViewModel _parent;
public TestElementViewModel Parent
{ get { return _parent; }
set { _parent = value; OnPropertyChanged("Parent"); }
}
public int Id
{
get { return Model.Id; }
set { Model.Id = value; OnPropertyChanged("Id"); }
}
// rest of the properties need wrapping too
}
makes it so that you don't have to manually assign the properties each time you instantiate a new viewmodel.