WPF MVVM how to show data from many tables in one view

Question

Hi,

I think this is very common scenario when you have relational database and classes witch represent each table as class (as is model)

  public class Role : AppEntityBase  
    {  
        public int RoleId { get; set; }  
        public string RoleName { get; set; }  
  
    }public class Person : AppEntityBase  
    {  
        public int PersonId { get; set; }   
        public string FirstName { get; set; }   
        public string LastName { get; set; }  
        //Foreign key  
        public int RoleId { get; set; }  
    }  
 public class PersonDetail : AppEntityBase  
    {  
        public int PersonDetailId { get; set; }  
        public int PersonId { get; set; }//FOREIGN KEY TO TABLE PERSON  
        public string Detail_1 { get; set; }  
        public string Detail_2 { get; set; }  
        public string Detail_3 { get; set; }  
        public string Detail_4 { get; set; }  
    }  
 public class AppEntityBase : SqlServerEntityBase   
    {  
        public DateTime CreateDateTime { get; set; }   
        public string CreateBy { get; set; }  
        public DateTime? UpdateDateTime { get; set; }  
        public string UpdateBy { get; set; }  
        public DateTime ValidFromDate { get; set; }  
        public DateTime? ValidToDate { get; set; }   
    }  

What is the best approach to show all data in single view?

Write query with joining all 3 table Role Person PersonDetail is not option bcz of using reflection when colling sql database.

Answer 1

Hi Igor,
you can extend Person class via partial keyword to add property with reference to PersonDetail.

Try 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"/>  
        <DataGridTextColumn Header="Detail 1" Binding="{Binding Detail.Detail_1}"/>  
      </DataGrid.Columns>  
    </DataGrid>  
  </Grid>  
</Window>  

Code:

using System;  
using System.Collections.Generic;  
using System.Linq;  
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" });  
      for (int i = 1; i < 100; i++) colPersonDetails.Add(new PersonDetail() { PersonDetailId = i, PersonId = rnd.Next(1, 10), Detail_1 = $"Detail {i}" });  
      //  
      // connect data items  
      foreach (var person in colPersons)  
      {  
        var req = from det in colPersonDetails where det.PersonId == person.PersonId orderby det.PersonDetailId descending select det;  
        if (req.Count() > 0) person.Detail = req.First();  
      }  
    }  
    private List<Person> colPersons = new List<Person>();  
    private List<Role> colRoles = new List<Role>();  
    private List<PersonDetail> colPersonDetails = new List<PersonDetail>();  
    public List<Person> Persons { get => colPersons; }  
    public List<Role> Roles { get => colRoles; }  
  }  
  
  public partial class Person  
  {  
    public PersonDetail Detail { get; set; }  
  }  
  
  public partial 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; }  
  }  
  public class PersonDetail  
  {  
    public int PersonDetailId { get; set; }  
    public int PersonId { get; set; }//FOREIGN KEY TO TABLE PERSON  
    public string Detail_1 { get; set; }  
  }  
}  

Result: