Question

I’m trying to bind a string to my textbox control, but the string is buried away.

The code I want to use is the following contrived example

namespace BackUps.Logging.ViewModel
{
    class Obj1
    {
        public Obj2 obj2 { get; set; }
    }

    class Obj2
    {
        public Obj3 obj3 { get; set; }
    }

    class Obj3
    {
        public string Message 
        {
           get { return "Hello World"; }
        }
}

My VM looks like

namespace BackUps.Logging.ViewModel
{
    internal class LogsVM
    {
       public Obj1 Obj1 { get; private set; }

    public LogsVM()
    {
          Obj1 = new Obj1();
    }
}

My question is, how can I bind the Message to the TextBlock with Xaml? This is what I have:

   <Window x:Class="BackUps.Logging.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:myData ="clr-namespace:BackUps.Logging.ViewModel"
        Title="Logging Results" Height="350" Width="525">

    <Grid DataContext="{x:Type myData:LogsVM}">
        <TextBlock Text="{Binding Message}" />
    </Grid>
</Window>

The above doesn’t work. Nor does

<TextBlock Text="{Binding Obj1.Message}" />

or

<TextBlock Text="{Binding Obj1.Obj2.Obj3.Message}" />

I know this example is daft, but there are many times when a class’s properties is a List type, and within that List is another etc, and knowing how to drill down to a specific property, no matter how many layers deep is important but I’ve gotten no where finding out how.

Answer 1

This works assuming the datacontext is your viewmodel:

<Window x:Class="WpfGridColumns.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" SizeToContent="WidthAndHeight"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:wpfGridColumns="clr-namespace:WpfGridColumns"
        d:DataContext="{d:DesignInstance Type=wpfGridColumns:LogsVM, IsDesignTimeCreatable=True}"
        >
    <Grid>
        <TextBox Text="{Binding Obj1.obj2.obj3.Message}" />
    </Grid>
</Window>

You can set up designtime data using this syntax:

d:DataContext="{d:DesignInstance Type=wpfGridColumns:LogsVM, IsDesignTimeCreatable=True}"

It gives Intellisense in the VS designer and is helpful when placing bindings.

I used this code behind:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = new LogsVM();
    }
}

internal class LogsVM
{
    public Obj1 Obj1 { get; private set; }

    public LogsVM()
    {
        Obj1 = new Obj1();
    }
}

public class Obj1
{
    public Obj1()
    {
        obj2=new Obj2();
    }
    public Obj2 obj2 { get; set; }
}

public class Obj2
{
    public Obj2()
    {
        obj3= new Obj3();
    }
    public Obj3 obj3 { get; set; }
}

public class Obj3
{
    public Obj3()
    {
        Message = "Test";
    }
    public string Message { get; set; }
}