I have created a combo box with data binding in WPF. I am not sure how to get value and set value of “comboboxselecteditem”

Question

This my Xaml code for combo box with data binding :

Answer 1

You can get and set the ComboBox's SelectedItem by binding to it, just as you bound the items of the ComboBox.

It is a good practice to put the data members for your UI into a separate class. This is typically done in a view model using the MVVM (Model, View, View Model) paradigm.

Something like this:

class ViewModel : INotifyPropertyChanged
{
    private ObservableCollection<CUSTOMER> _customers = new ObservableCollection<CUSTOMER>();
    public IList<CUSTOMER> Customers
    {
        get { return _customers; }
    }

    private CUSTOMER _selectedCustomer = null;
    public CUSTOMER SelectedCustomer
    {
        get { return _selectedCustomer; }
        set
        {
            _selectedCustomer = value;
            OnPropertyChanged("SelectedCustomer");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void OnPropertyChanged(string propName)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propName));
    }
}

And in your window class:

class MainWindow
{
    public MainWindow()
    {
        InitializeComponent();

        DataContext = new ViewModel();
    }
}

And finally in your XAML:

<ComboBox ItemsSource="{Binding Path=Customers}"
          SelectedItem="{Binding Path=SelectedCustomer, Mode=TwoWay}">
    ...
</ComboBox>

I would also move the code that loads the customers from the database into the ViewModel, and once done set the SelectedCustomer property to a reasonable default. For example, to select the customer whose name is Bob, run the following once the objects have been loaded from the database:

SelectedCustomer = _customers.FirstOrDefault(customer => customer.CUSTOMER_NAME.Equals("Bob"));

Answer 2

You could cast the SelectedItem property of the ComboBox to a CUSTOMER object to get the currently selected item:

CUSTOMER selectedCustomer = C1.SelectedItem as CUSTOMER;
if(selectedCustomer != null)
    MessageBox.Show(selectedCustomer.CUSTOMER_NAME);

To select an item you set the SelectedItem property to a CUSTOMER object that is included in the ComboBox's ItemsSource:

C1.SelectedItem = C1.Items[0]; //selects the first customer (index = 0)

Or if you know the name or description of the customer:

string theName = "some customer name...";
C1.SelectedItem = C1.Items.OfType<CUSTOMER>().FirstOrDefault(x => x.CUSTOMER_NAME == theName);