Binding a button in WPF using PRISM DelegateCommand - wpf

Question

I am just starting to learn WPF using the PRISM library. Please help me to solve one question. How to bind a button using DelegateCommand?
In the code behind everything is fine. In the MVVM code I can't get it to work.
Thanks.
My code in XAML:
<UserControl x:Class="Panel.Modules.DockingManager.DockingManagerPanel.DockingManagerPanelPrism"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:prism="http://prismlibrary.com/"
xmlns:system="clr-namespace:System;assembly=System.Runtime"
prism:ViewModelLocator.AutoWireViewModel="True">
<Grid>
<Button x:Name="button"
Command="{Binding LoadAllFiles}"
CommandTarget="{Binding ElementName=textBox}"
Height="24" Width="24">
</Button>
<TextBox x:Name="textBox" </TextBox>
</Grid>
</UserControl>
And my code in ViewModel:
public class DockingManagerPanelViewModel : BindableBase
{
public DelegateCommand LoadAllFiles { get; set; }
public DockingManagerPanelViewModel()
{
LoadAllFiles = new DelegateCommand(LoadTxt);
}
private void LoadTxt()
{
var dialog = new Microsoft.Win32.OpenFileDialog();
dialog.Multiselect = true;
dialog.FileName = "Document";
dialog.DefaultExt = ".txt";
dialog.Filter = "Text documents (*.*)|*.*";
bool? result = dialog.ShowDialog();
if (result == true)
{
StreamReader sr = new StreamReader(File.OpenRead(dialog.FileName));
sr.ReadToEnd();
}
}
}

Answer 1

You are reading the text but not doing anything with what you read. You need to read it into some sort of string property and then bind the TextBox to that property.
Also you are failing to use a using statement on the StreamReader.
The good news is that you don't need to use StreamReader. You can just use the much simpler File.ReadAllText function.
First, add this to your view model. A public property exposing the read text. It uses BindableBase's SetProperty to raise the proper event when the value changes
public string LoadedText
{
get => _loadedText;
set => SetProperty(ref _loadedText, value);
}
private string _loadedText = string.Empty;
Next, change the last few lines of your LoadTxt function to do this instead of using StreamReader
if (result == true)
LoadedText = File.ReadAllText(dialog.FileName)
Finally, change the TextBox in XAML to look like this. I made it one way becase I assume you do not want the user editing inside of it, to change the value in the backing LoadedText property. A better approach might be to just use a TextBlock instead of a TextBox
<TextBox x:Name="textBox" Text="{Binding LoadedText, Mode=OneWay}"/>