WPF MVVM relational database with foreign keys sample

Question

Hi what is the best practice to work with foreign keys?
How to design object class?

Should I use valueConverter to switch between RoleId to RoleName

Answer 1

Hi Igor
for displaying you can use readonly ComboBoxColumn like in following demo:

XAML:

<Window x:Class="WpfApp1.Window018"  
        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:WpfApp018"  
        mc:Ignorable="d"  
        Title="Window018" Height="450" Width="800">  
  <Window.Resources>  
    <local:ViewModel x:Key="vm"/>  
  </Window.Resources>  
  <Grid DataContext="{StaticResource vm}">  
    <DataGrid ItemsSource="{Binding Persons}" AutoGenerateColumns="false">  
      <DataGrid.Columns>  
        <DataGridTextColumn Header="ID" Binding="{Binding PersonId}"/>  
        <DataGridTextColumn Header="Firstname" Binding="{Binding FirstName}"/>  
        <DataGridComboBoxColumn Header="Role name"   
                                IsReadOnly="True"  
                                ItemsSource="{Binding Roles, Source={StaticResource vm}}"  
                                SelectedValueBinding="{Binding RoleId}"  
                                SelectedValuePath="RoleId"  
                                DisplayMemberPath="RoleName"/>  
      </DataGrid.Columns>  
    </DataGrid>  
  </Grid>  
</Window>  

Classes:

using System;  
using System.Collections.Generic;  
using System.Windows;  
  
namespace WpfApp018  
{  
  public class ViewModel  
  {  
    public ViewModel()  
    {  
      Random rnd = new Random();  
      for (int i = 1; i < 10; i++) colPersons.Add(new Person() { PersonId = i, FirstName = $"First name {i}", RoleId = rnd.Next(1, 5) });  
      colRoles.Add(new Role() { RoleId = 1, RoleName = "Admin" });  
      colRoles.Add(new Role() { RoleId = 2, RoleName = "User" });  
      colRoles.Add(new Role() { RoleId = 3, RoleName = "Member" });  
      colRoles.Add(new Role() { RoleId = 4, RoleName = "Owner" });  
    }  
    private List<Person> colPersons = new List<Person>();  
    private List<Role> colRoles = new List<Role>();  
    public List<Person> Persons { get => colPersons; }  
    public List<Role> Roles { get => colRoles; }  
  }  
  
  public class Person  
  {  
    public int PersonId { get; set; }  
    public string FirstName { get; set; }  
  
    public int RoleId { get; set; }  
  }  
  public class Role  
  {  
    public int RoleId { get; set; }  
    public string RoleName { get; set; }  
  }  
}  

Result:

Answer 2

Hi Peter thanx for that answer.
I have another scenario where we have another table PersonDetail

And I want to show last valid row (history track details one person have many personDetail)....

in this scenario we have data from 3 tables. should I create DTO witch have all data in one class (super class PersonRoleDetail) and then use join on database to retrieve all needed data?

or is there some another way around to do this on front end side?

I use ADO.NET with reflection to load data (not manual mapping )