Adding multiple controls to grid through foreach-command at runtime (C# WPF)

A good day dear developers. My name is Danny.

This is my first post here on Stackoverflow... as much as i am fairly new to the .NET Framework. I did search quite thoroughly through several forums, but am apparently looking with my nose.

My question is this: I am writing a piece of script that reads out how many .txt-files there exist within a directory.

Then it creates the amount of GroupBoxes (with each a grid) as there are .txt's through a 'foreach' command. And within that same foreach-command, i use: Grid.Children.Add(control). Per foreach-iteration there are 2 controls to be added to the generated grid.

The problem: It does not do that... well sort of. It only makes 2 iterations, regardless of how many .txt's there are. And within the Output-dialog it says: A first chance exception of type 'System.Argu开发者_JS百科mentException' occurred in PresentationCore.dll.

In case my explanation is not as clear as i meant to, here follows my script, and thanks for reading:

using System;
using System.IO;
using System.Linq;
using System.Windows;
using System.Threading;
using System.Windows.Media;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Threading;
using System.Windows.Controls.Primitives;

namespace Notes
{
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }


    // Create Objects
    public TextBox tBox = new TextBox();
    public Label fLabel = new Label();
    public GroupBox group = new GroupBox();
    public Grid groupGrid = new Grid();


    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        // Global Variables
        int Increment = 1;
        string Dir = "DIRECTORY_HERE";
        int leftMargin = 10;
        int betweenMargin = 10;

        // GroupBox Initials
        group.Height = this.Height - 125;
        group.Margin = new Thickness(0, 75, 0, 0);
        group.HorizontalAlignment = HorizontalAlignment.Left;
        group.VerticalAlignment = VerticalAlignment.Top;

        // Grid Initials
        groupGrid.Width = leftMargin;
        groupGrid.Height = group.Height;
        groupGrid.Margin = new Thickness(0, 0, 0, 0);
        groupGrid.HorizontalAlignment = HorizontalAlignment.Left;
        groupGrid.VerticalAlignment = VerticalAlignment.Top;

        // Label Initials
        fLabel.Width = 260;
        fLabel.Height = 28;
        fLabel.HorizontalAlignment = HorizontalAlignment.Left;
        fLabel.VerticalAlignment = VerticalAlignment.Top;
        fLabel.Margin = new Thickness(0, 0, 0, 0);

        // TextBox Intitials
        tBox.Width = 100;
        tBox.Height = groupGrid.Height;
        tBox.VerticalScrollBarVisibility = ScrollBarVisibility.Hidden;
        tBox.HorizontalAlignment = HorizontalAlignment.Left;
        tBox.VerticalAlignment = VerticalAlignment.Top;
        tBox.Foreground = new SolidColorBrush(Colors.DarkCyan);
        tBox.Background = new SolidColorBrush(Colors.Red);
        tBox.TextWrapping = TextWrapping.NoWrap;



        // Get paths of all files within given directory.
        string[] Notes = Directory.GetFiles(Dir, "*.*", SearchOption.TopDirectoryOnly).ToArray();

        foreach (string Note in Notes)
        {
            Console.WriteLine("NOTE: " + Note);

            // Text settings
            FileInfo fi = new FileInfo(Note);
            TextReader tr = new StreamReader(fi.ToString());
            tBox.Name = "tBox" + Increment.ToString();
            tBox.Text = tr.ReadToEnd();
            tBox.Margin = new Thickness(betweenMargin, 0, 0, 0);

            // FileLabel settings
            fLabel.Name = "fLabel" + Increment.ToString();

            // GroupGrid settings
            groupGrid.Name = "groupGrid" + Increment.ToString();
            groupGrid.Children.Add(tBox);               //error
            groupGrid.Children.Add(fLabel);             //error

            // group settings
            group.Width = leftMargin + (tBox.Width * Increment) + (betweenMargin * Increment);
            group.Content = groupGrid;

            // Increment
            Increment++;
        }


        NotesDoc.Children.Add(group);
    }

You are attempting to program a WPF application like you would a Windows Forms app. Believe me, you can accomplish your goal much easier if you actually learn some of the WPF development patterns (such as MVVM).

For example, this can be easily accomplished using an ObservableCollection holding all (not sure how you are doing this) FileInfo instances (one for each file).

You then bind a ItemsControl's ItemsSource property to this collection. Now, whenever you add a new FileInfo instance to the ObservableCollection the ItemsControl will add a new row and bind that row to the instance.

Of course, the default template for each row just calls .ToString() on each instance, so you'll get a bunch of rows that contains "System.IO.FileInfo". To show information about each FileInfo, you can add a DataTemplate to ItemsSource.ItemTemplate and add controls that bind to the public properties of the FileInfo.

It is VERY important to understand some of these basic patterns when developing WPF applications. Attempting to interact with the UI from the codebehind in the manner you are attempting is VERY HARD to do. Many of the UI patterns for WPF applications are optimized for use in XAML; attempting to interact with these (such as attached properties) from the codebehind can be extremely confusing and counterintuitive.

Here's a simple MVVM sample I updated. To use this, create a new solution (3.5 or greater) called SimpleMVVM. Create a new class in the root of the project called ViewModel and add the following code to the file:

/// <summary>
/// A simple ViewModel to demonstrate MVVM
/// </summary>
public sealed class ViewModel : DependencyObject, IDataErrorInfo
{
    #region Properties
    #region DirectoryName
    /// <summary>
    /// The <see cref="DependencyProperty"/> for <see cref="DirectoryName"/>.
    /// </summary>
    public static readonly DependencyProperty DirectoryNameProperty =
        DependencyProperty.Register(
            DirectoryNameName,
            typeof(string),
            typeof(ViewModel),
            new UIPropertyMetadata(null));

    /// <summary>
    /// The name of the <see cref="DirectoryName"/> <see cref="DependencyProperty"/>.
    /// </summary>
    public const string DirectoryNameName = "DirectoryName";

    /// <summary>
    /// 
    /// </summary>
    public object DirectoryName
    {
        get { return (object)GetValue(DirectoryNameProperty); }
        set { SetValue(DirectoryNameProperty, value); }
    }
    #endregion

    #region SelectedFile
    /// <summary>
    /// The <see cref="DependencyProperty"/> for <see cref="SelectedFile"/>.
    /// </summary>
    public static readonly DependencyProperty SelectedFileProperty =
        DependencyProperty.Register(
            SelectedFileName,
            typeof(FileInfo),
            typeof(ViewModel),
            new UIPropertyMetadata(null));

    /// <summary>
    /// The name of the <see cref="SelectedFile"/> <see cref="DependencyProperty"/>.
    /// </summary>
    public const string SelectedFileName = "SelectedFile";

    /// <summary>
    /// 
    /// </summary>
    public FileInfo SelectedFile
    {
        get { return (FileInfo)GetValue(SelectedFileProperty); }
        set { SetValue(SelectedFileProperty, value); }
    }
    #endregion


    /// <summary>
    /// The files found under <see cref="DirectoryName"/>.
    /// </summary>
    public ObservableCollection<FileInfo> Files { get; private set; }

    /// <summary>
    /// Holds the last filename error for IDataErrorInfo
    /// </summary>
    private string _lastDirectoryNameError = null;
    #endregion

    #region ctor
    /// <summary>
    /// Initializes a new instance of the <see cref="ViewModel"/> class.
    /// </summary>
    public ViewModel()
    {
        Files = new ObservableCollection<FileInfo>();
    }
    #endregion

    #region methods
    /// <summary>
    /// Invoked whenever the effective value of any dependency property on this <see cref="T:System.Windows.DependencyObject"/> has been updated. The specific dependency property that changed is reported in the event data.
    /// </summary>
    /// <param name="e">Event data that will contain the dependency property identifier of interest, the property metadata for the type, and old and new values.</param>
    protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
    {
        base.OnPropertyChanged(e);
        if (e.Property == DirectoryNameProperty)
            UpdateFiles(e.OldValue as string, e.NewValue as string);
    }

    /// <summary>
    /// Updates <see cref="Files"/> when <see cref="DirectoryName"/> changes.
    /// </summary>
    /// <param name="oldDirectoryName">The old value of <see cref="DirectoryName"/></param>
    /// <param name="newDirectoryName">The new value of <see cref="DirectoryName"/></param>
    private void UpdateFiles(string oldDirectoryName, string newDirectoryName)
    {
        if (string.IsNullOrWhiteSpace(newDirectoryName))
        {
            Files.Clear();
            return;
        }
        if (!string.IsNullOrEmpty(oldDirectoryName) &&
            oldDirectoryName.Equals(newDirectoryName, StringComparison.OrdinalIgnoreCase))
            return;

        try
        {
            var di = new DirectoryInfo(Directory.Exists(newDirectoryName) ? newDirectoryName : Path.GetDirectoryName(newDirectoryName));
            // dirty hack
            if (di.ToString().Equals(".", StringComparison.OrdinalIgnoreCase))
            {
                _lastDirectoryNameError = "Not a valid directory name.";
                return;
            }
            Files.Clear();
            foreach (var file in di.GetFiles())
                Files.Add(file);
            _lastDirectoryNameError = null;
        }
        catch (Exception ioe)
        {
            _lastDirectoryNameError = ioe.Message;
        }
    }
    #endregion

    #region IDataErrorInfo
    /// <summary>
    /// Gets an error message indicating what is wrong with this object.
    /// </summary>
    /// <returns>An error message indicating what is wrong with this object. The default is an empty string ("").</returns>
    string IDataErrorInfo.Error
    {
        get
        {
            return _lastDirectoryNameError;
        }
    }

    /// <summary>
    /// Gets the error message for the property with the given name.
    /// </summary>
    /// <returns>The error message for the property. The default is an empty string ("").</returns>
    string IDataErrorInfo.this[string columnName]
    {
        get
        {
            if (columnName.Equals(DirectoryNameName, StringComparison.OrdinalIgnoreCase))
                return _lastDirectoryNameError;
            return null;
        }
    }
    #endregion
}

Next, open MainWindow.xaml and replace the xaml with the following:

<Window
    x:Class="SimpleMVVM.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:t="clr-namespace:SimpleMVVM"
    Title="MainWindow"
    Height="350"
    Width="525">
    <Window.DataContext>
        <t:ViewModel />
    </Window.DataContext>
    <Window.Resources>
        <Style
            x:Key="alternatingListViewItemStyle"
            TargetType="{x:Type ListViewItem}">
            <Style.Triggers>
                <Trigger
                    Property="ItemsControl.AlternationIndex"
                    Value="1">
                    <Setter
                        Property="Background"
                        Value="LightGray"></Setter>
                </Trigger>
                <Trigger
                    Property="ItemsControl.AlternationIndex"
                    Value="2">
                    <Setter
                        Property="Background"
                        Value="White"></Setter>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition
                Height="auto" />
            <RowDefinition />
            <RowDefinition
                Height="auto" />
        </Grid.RowDefinitions>
        <TextBox
            Margin="4"
            Text="{Binding DirectoryName, ValidatesOnDataErrors=True, ValidatesOnExceptions=True,UpdateSourceTrigger=PropertyChanged}">
            <TextBox.Style>
                <Style
                    TargetType="TextBox">
                    <Setter
                        Property="ToolTip"
                        Value="Please enter a directory name" />
                    <Style.Triggers>
                        <Trigger
                            Property="Validation.HasError"
                            Value="true">
                            <Setter
                                Property="ToolTip"
                                Value="{Binding (Validation.Errors)[0].ErrorContent, RelativeSource={x:Static RelativeSource.Self}}" />
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </TextBox.Style>
        </TextBox>
        <ListView
            Margin="4"
            Grid.Row="1"
            AlternationCount="2"
            ItemsSource="{Binding Files}"
            ItemContainerStyle="{StaticResource alternatingListViewItemStyle}"
            SelectedItem="{Binding SelectedFile}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition />
                            <RowDefinition />
                            <RowDefinition />
                            <RowDefinition />
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition
                                Width="100" />
                            <ColumnDefinition />
                        </Grid.ColumnDefinitions>
                        <Label
                            Grid.Row="0">Name</Label>
                        <Label
                            Grid.Row="1">Size</Label>
                        <Label
                            Grid.Row="2">Read Only</Label>
                        <Label
                            Grid.Row="3">Type</Label>
                        <TextBlock
                            Grid.Row="0"
                            Grid.Column="1"
                            Text="{Binding Name}" />
                        <TextBlock
                            Grid.Row="1"
                            Grid.Column="1"
                            Text="{Binding Length}" />
                        <CheckBox
                            Grid.Row="2"
                            Grid.Column="1"
                            IsChecked="{Binding IsReadOnly}"
                            IsEnabled="False" />
                        <TextBlock
                            Grid.Row="3"
                            Grid.Column="1"
                            Text="{Binding Extension}" />
                    </Grid>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
        <StatusBar
            Grid.Row="2">
            <StatusBarItem
                Content="{Binding SelectedFile.FullName, StringFormat='Selected: {0}', FallbackValue='Please enter a directory and select a file.'}" />
        </StatusBar>
    </Grid>
</Window>

(excuse me everybody for the code dump!) Compile, fix errors and run it.

You have to create new instances of tbox and fLabel inside the loop, and maybe of groupGrid as well.

foreach (string Note in Notes)
{
  var box = new TextBox();
  var lbl = new Label();
  // markup properties ....
}

If you don't need a new groupBox each turn, then don't change its name either.