ComboBox Binding with two different properties from two different classes in MVVM C#

Question

I had to rewrite my problem. The blackquoted part below is this post before the edit.

I have two properties : capacitiveCurrent and ShowProductSum. Before any changes in my MVVM application I used to bind capacitiveCurrent with a value that was set in the contructor - it was 15 always.

capacitiveCurrent is placed in a different class LineOut, code :

capacitiveCurrent property

    private double _capacitiveCurrent;
    public double CapacitiveCurrent
    {
        get { return _capacitiveCurrent; }
        set
        {
            if (_capacitiveCurrent != value)
            {
                _capacitiveCurrent = value;
                OnPropertyChanged("_capacitiveCurrent");
            }
        }
    }

The second property is placed in MainWindow.xaml.cs code:

ShowProductSum

        public double _showProductSum;
    public double ShowProductSum
    {
        get { return _showProductSum; }
        set
        {
            if (_showProductSum != value)
            {
                _showProductSum = value;
                OnPropertyChanged("ProductSum");
            }
        }
    }

The logic behing setting and getting ShowProductSum is done.. almost. But what I expect from those two properties is that I want them to show up in the ComboBox. This is what I have:

    private ObservableCollection<double> _comboBoxCapacitiveCurrent = new ObservableCollection<double>();
    public ObservableCollection<double> ComboBoxCapacitiveCurrent
    {
        get
        {
            _comboBoxCapacitiveCurrent.Clear();
            _comboBoxCapacitiveCurrent.Add(lineWy.capacitiveCurrent);
            _comboBoxCapacitiveCurrent.Add(ShowProductSum);
            return _comboBoxCapacitiveCurrent;
        }
        set
        {
            if (_comboBoxCapacitiveCurrent != value)
            {
                _comboBoxPradPojemnosciowy = value;
                OnPropertyChanged("ComboBoxCapacitiveCurrent");
            }
        }
    }
    public double SelectedItem { get; set; }

ComboBox:

      <DataGridTemplateColumn Header="Capacitive Current " HeaderStyle="{StaticResource ZwarcioweHeaderStyle}">
      <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
         <ComboBox 
                  ItemsSource="{Binding Path=ComboBoxCapacitiveCurrent}"
                  SelectedValue="{Binding Path=SelectedItem, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
          >
                  </ComboBox>
         </DataTemplate></DataGridTemplateColumn.CellTemplate></DataGridTemplateColumn>

CombBox is present but nothing is in the dropdownlist of combobox.Some blank space just underneath this combobox. Everything implements INotifyPropertyChanged interface.

Thanks in advance.

I'm an absolute beginner in MVVM C#. I'm trying to bind two properties which are located in two different classes.

First property is public double capacitiveCurrent { get; set; } from one class and until then I used this property to View it with a normal binding - the initialized value was shown.

 public double productLengthShortCircuitCurrent
    {
    get { return length* capacitiveShortCircuitCurrentwithGround; }
    set { }
    } is a combination of the two `length` and `capacitiveShortCircuitCurrentwithGround` both with getters and

setters.

ComboBox is placed inside

`<DataGridTemplateColumn Header"ABC">
  <DataGridTemplateColumn.CellTemplate
   <DataTemplate>
    <ComboBox .../>`

What I'm trying to do is having those two properties listed in a ComboBox and:

1. I need capacitiveCurrent to be editable from the View,

2. The productLengthShortCircuitCurrent should be a sum of all the set values ( so a sum product).. should I call a function to do such and then bind it to the ComboBox?

**I've maged to set and get this property and achieved to get the ProductSum property below.. It is all about displaying the two properties in a ComboBox.

I'm really confused. Searched for an answer for two days, didn't come up with an idea. Maybe me knowledge is to shallow but... Tried to bind those two properties to an interface with something like public IConnectedProperties Categories and a private _category list with getter and setter.

Answer 1

Put your two instances of your classes in one viewmodel class and bind it to the appropriate value. “ViewModels” are used to communicate between the Views and the Models. So put all your logic for interacting with the view in the viewmodel. Then you have to bind your viewmodel to the view and your datacontext is set on the object. If you want to bind your property in the instance you can use Instance.Property for the binding

Maybe these will help you. For basic explanation

Answer 2

Fix this in your setter:

_comboBoxPradPojemnosciowy = value; // binding will loose the instance

Use "Clear()" and "Add()". When you change the instance - binding is still looking in the old instance.

_comboBoxPradPojemnosciowy.Clear();
foreach (var item in value)
{
    _comboBoxPradPojemnosciowy.Add(item);
}

OnPropertyChanged("ComboBoxCapacitiveCurrent");

If ShowProductSum part is working, maybe this is the only thing you need to fix.

ComboBox bindings:

ItemsSource="{Binding Path=ComboItems}"   
SelectedItem="{Binding Path=SelectedItem}"

Carete properties and fields:

private ObservableCollection<double> comboItems = new ObservableCollection<double>();
public ObservableCollection<double> ComboItems{
    get
    {
        this.comboItems.Clear();
        this.comboItems.Add(prad_pojemnosciowy);
        this.comboItems.Add(iloczyn_dlugosc_pojemnościowy_prąd_zwarcia_z_ziemią);
        return this.comboItems;
    } 
    set;
}
public double SelectedItem{get;set}

Remember to notify property changed for "ComboItems" in the setters of the two properties.