Question

I am fairly new to MVVM, so bear with. I have a view model class that has a public property implemented as so:

public List<float> Length
{
  get;
  set;
}

In my XAML for the view, I have several text boxes, with each one bound to a specific element in this Length list:

  <TextBox Text="{Binding Length[0], Converter=DimensionConverter}" />
  <TextBox Text="{Binding Length[2], Converter=DimensionConverter}" />
  <TextBox Text="{Binding Length[4], Converter=DimensionConverter}" />

The DimensionConverter is a IValueConverter derived class that formats the values like a dimension (i.e. 480.0 inches becomes 40’0″ in the text box on screen), and back again (i.e. takes 35’0″ for a string and yield 420.0 inches for the source)

My issue: I need to be able to validate each value in the List as it is changed in the associated TextBox. For some, I may need to modify other values in the List depending on the entered value (i.e. change the float at Length[0] will change the value at Length[4] and update the screen).

Is there any way to re-work the property to allow for an indexer? Or, do I need to create individual properties for each item in the List (which really makes the List unnecessary)? Essentially, since I already have the collection of float, I was hoping to be able to write MVVM code to validate each item as it is modified.

Thoughts? (and, thanks in advance)

Answer 1

You can use an ObservableCollection<float> instead of a List<float>, and handle the CollectionChanged event to detect when the user changes a value.