populate cascading combobox with Entity Framework

Question

This is a MSDN question asked by zleug, the source is populate cascading combobox with Entity Framework.

Hi All.

I created simple WPF form with two ComboBoxes. I populated one ComboBox

public List<Customer> GetApplication()
        {
            using (CustModel customer = new CustModel())
            {
                List<Customer> cust = customer.Customers.Distinct().ToList();

                cust.Insert(0, new Customer
                {
                    CustomerID = "0",
                    ContactName = "Please select"
                });

                //Assign Entity as DataSource.
                cbCustomer.ItemsSource = cust;
                cbCustomer.DisplayMemberPath = "ContactName";
                cbCustomer.SelectedValue = "CustomerID";
                cbCustomer.Text = "Please select";

                return cust;
            }
        }

How to select in the List only ContactName column and distinct it?

In SQL look like: SELECT distinct [ContactName] FROM Customer

And how populate second ComboBox depended from section from first Combobox?

Thanks.

Answer 1

Hi,

Welcome to our Microsoft Q&A platform!

The reply form Peter Fleischer

Xaml:

<Window x:Class="WpfApp1.Window10"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp10"
        mc:Ignorable="d"
        Title="Window10" Height="450" Width="800">
  <Window.DataContext>
    <local:ViewModel/>
  </Window.DataContext>
  <Grid>
    <DataGrid ItemsSource="{Binding View}"/>
  </Grid>
</Window>

ViewModel:

using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Data;

namespace WpfApp10
{
  public partial class ViewModel
  {
    public ViewModel()
    {
      cvs.Source= from item in (new WpfApp1.DemoDBEntities()).Tab1.AsEnumerable() select item;
    }
    CollectionViewSource cvs = new CollectionViewSource();
    public ICollectionView View { get => cvs.View; }
  }
}

In demo I use catalog "Demo" with table "Tab1".

Thanks.