WPF Behaviors no longer working with newest NuGets.

Stout 286 Reputation points
2021-06-29T17:32:17.07+00:00

Hi. The app used to work fine, but a few weeks ago we updated hundreds of NuGet packages. We recently discovered that any reference to a WPF Behavior gives the following error:

System.Windows.Markup.XamlParseException: ''Add value to collection of
type 'Microsoft.Xaml.Behaviors.BehaviorCollection' threw an
exception.' Line number '78' and line position '86'.'

Inner Exception ArgumentException: Cannot add instance of type
'TextBoxInputBehavior' to a collection of type 'BehaviorCollection'.
Only items of type 'T' are allowed.

I suspect this is because of a NuGet update, but I don't know which one had caused the error, or which need to be changed. I'm using the latest version for Microsoft.Xaml.Behaviors.Wpf (1.1.31).

I would appreciate advice. Thanks.

Code:

         xmlns:Behaviors="clr-namespace:MyCompany.MyProject"
         xmlns:i="http://schemas.microsoft.com/xaml/behaviors"

            <TextBox Text="...">
                <i:Interaction.Behaviors>
                    <Behaviors:TextBoxInputBehavior InputMode="DecimalInput" JustPositiveDecimalInput="False" RangeMin="-1000000.000" RangeMax="1000000.000" />
                </i:Interaction.Behaviors>
            </TextBox>

Edit: TextBoxInputBehavior below. Looks like it's been copied as-is from here.

using Microsoft.Xaml.Behaviors;

public class TextBoxInputBehavior : Behavior<TextBox>
{
    const NumberStyles validNumberStyles = NumberStyles.AllowDecimalPoint |
                                               NumberStyles.AllowThousands |
                                               NumberStyles.AllowLeadingSign;
    public TextBoxInputBehavior()
    {
        this.InputMode = TextBoxInputMode.None;
        this.JustPositivDecimalInput = false;
    }

    public TextBoxInputMode InputMode { get; set; }


    public static readonly DependencyProperty JustPositivDecimalInputProperty =
     DependencyProperty.Register("JustPositivDecimalInput", typeof(bool),
     typeof(TextBoxInputBehavior), new FrameworkPropertyMetadata(false));

    public bool JustPositivDecimalInput
    {
        get { return (bool)GetValue(JustPositivDecimalInputProperty); }
        set { SetValue(JustPositivDecimalInputProperty, value); }
    }

    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.PreviewTextInput += AssociatedObjectPreviewTextInput;
        AssociatedObject.PreviewKeyDown += AssociatedObjectPreviewKeyDown;

        DataObject.AddPastingHandler(AssociatedObject, Pasting);

    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.PreviewTextInput -= AssociatedObjectPreviewTextInput;
        AssociatedObject.PreviewKeyDown -= AssociatedObjectPreviewKeyDown;

        DataObject.RemovePastingHandler(AssociatedObject, Pasting);
    }

    private void Pasting(object sender, DataObjectPastingEventArgs e)
    {
        if (e.DataObject.GetDataPresent(typeof(string)))
        {
            var pastedText = (string)e.DataObject.GetData(typeof(string));

            if (!this.IsValidInput(this.GetText(pastedText)))
            {
                System.Media.SystemSounds.Beep.Play();
                e.CancelCommand();
            }
        }
        else
        {
            System.Media.SystemSounds.Beep.Play();
            e.CancelCommand();
        }
    }

    private void AssociatedObjectPreviewKeyDown(object sender, KeyEventArgs e)
    {
        if (e.Key == Key.Space)
        {
            if (!this.IsValidInput(this.GetText(" ")))
            {
                System.Media.SystemSounds.Beep.Play();
                e.Handled = true;
            }
        }
    }

    private void AssociatedObjectPreviewTextInput(object sender, TextCompositionEventArgs e)
    {
        if (!this.IsValidInput(this.GetText(e.Text)))
        {
            System.Media.SystemSounds.Beep.Play();
            e.Handled = true;
        }
    }

    private string GetText(string input)
    {
        var txt = this.AssociatedObject;

        int selectionStart = txt.SelectionStart;
        if (txt.Text.Length < selectionStart) 
            selectionStart = txt.Text.Length;

        int selectionLength = txt.SelectionLength;
        if (txt.Text.Length < selectionStart + selectionLength) 
            selectionLength = txt.Text.Length - selectionStart;

        var realtext = txt.Text.Remove(selectionStart, selectionLength);

        int caretIndex = txt.CaretIndex;
        if (realtext.Length < caretIndex) 
            caretIndex = realtext.Length;

        var newtext = realtext.Insert(caretIndex, input);

        return newtext;
    }

    private bool IsValidInput(string input)
    {
        switch (InputMode)
        {
            case TextBoxInputMode.None:
                return true;
            case TextBoxInputMode.DigitInput:
                return CheckIsDigit(input);

            case TextBoxInputMode.DecimalInput:
                decimal d;
                //wen mehr als ein Komma
                if (input.ToCharArray().Where(x => x == ',').Count() > 1)
                    return false;

                if (input.Contains("-"))
                {
                    if (this.JustPositivDecimalInput) 
                        return false;

                    //minus einmal am anfang zulässig
                    if (input.IndexOf("-",StringComparison.Ordinal) == 0  && input.ToCharArray().Count(x=>x=='-') == 1)
                        return true;
                }

                var result = decimal.TryParse(input, validNumberStyles, CultureInfo.CurrentCulture, out d);
                return result;



            default: throw new ArgumentException("Unknown TextBoxInputMode");

        }
        return true;
    }

    private bool CheckIsDigit(string wert)
    {
        return wert.ToCharArray().All(Char.IsDigit);
    }
}

public enum TextBoxInputMode
{
    None,
    DecimalInput,
    DigitInput
}
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