WPF combobox binding and SelectedItem

Question

I have a list containing instances of the following class:

namespace Foo.InformationModel.Reference
{
    public class ReferenceCodeTypeChar
    {
        public ReferenceCodeTypeChar();

        public string Category { get; set; }
        public string CodeValue { get; set; }
        public string Description { get; set; }
        public string Value { get; set; }
    }
}

Here is the object that is used as the DataContext for the window in which the combobox is and its related properties:

public class MyObject
{
    public List<Foo.InformationModel.Reference.ReferenceCodeTypeChar> ProgramTypes() {...}

    private string _selectedProgramTypeCode;
    public string SelectedProgramTypeCode
    {
        get
        {
            return _selectedProgramTypeCode;
        }
        set
        {
            if (_selectedProgramTypeCode != value)
            {
                _selectedProgramTypeCode = value;
                OnPropertyChanged("SelectedProgramTypeCode");
            }
        }
    }
}

Here is the xaml code behind for the combobox:

<ComboBox ItemsSource="{Binding Path=ProgramTypes}"
          SelectedItem="{Binding Path=SelectedProgramTypeCode, Mode=TwoWay}"
          DisplayMemberPath="Description"
          SelectedValuePath="Value"/>

The problem happens inside SelectedProgramTypeCode. The value of the "value" variable is Foo.InformationModel.Reference.ReferenceCodeTypeChar instead of the expected string of Value property of the ReferenceCodeTypeChar object. What is wrong?

@Hopeless You should write this as an answer, because it is true. — Michael Mairegger, Oct 06 '15 at 15:16
well I was wrong with a quick glance at the XAML. Looks like the `SelectedItem` is bound wrong. It should be bound to a property of type `Foo.InformationModel.Reference.ReferenceCodeTypeChar`, in this case you bind it to a string property. In the way from `SelectedItem` to `SelectedProgramTypeCode`, there is no Converter, so `ToString()` will be called on `SelectedItem` and resolved to `"Foo.InformationModel.Reference.ReferenceCodeTypeChar"` before being set to `SelectedProgramTypeCode` (so you see it in `value` variable). — Hopeless, Oct 06 '15 at 15:31

score 3 · Answer 1 · edited May 23 '17 at 12:08

3

You have to use SelectedItem or SelectedValuePath in conjunction with SelectedValue.

See this answer Difference between SelectedItem, SelectedValue and SelectedValuePath

edited May 23 '17 at 12:08

Community

1
1

answered Oct 06 '15 at 15:04

Giangregorio

1,482
2
11
12

score 0 · Answer 2 · answered Oct 06 '15 at 15:13

You should have used SelectedValue instead of SelectedItem in your XAML.

<ComboBox 
  ItemsSource="{Binding Path=ProgramTypes}"
  SelectedValue="{Binding Path=SelectedProgramTypeCode, Mode=TwoWay}"
  DisplayMemberPath="Description"
  SelectedValuePath="Value" />

WPF combobox binding and SelectedItem

2 Answers2