WPF中的绑定验证

Question

I am jumping into Binding Validation for the first time in WPF. I was using the tutorial guides in the Microsoft Docs for validating data entered into a textbox. I believe I understand it and followed the process correctly however the validation is still not working. I am not sure if the Binding on the textbox is wrong or if something is amiss with my ValidationRule. Any help would be appreciated.

Below is the class with the validator rule.

class NumberCansValidationRule : ValidationRule
{
    private int _min;
    private int _max;

    public int Min
    {
        get { return _min; }

        set { _min = value; }
    }

    public int Max
    {
        get { return _max; }

        set { _max = value; }
    }

    public override ValidationResult Validate(object value, CultureInfo cultureInfo)
    {
        int numCans = 0;

        try
        {
            if (((string)value).Length > 0)
            {
                numCans = Int32.Parse((string)value);
            }
        }
        catch (Exception e)
        {
            return new ValidationResult(false, "Illegal characters or " + e.Message);
        }


        if ((numCans < Min) || (numCans > Max))
        {
            return new ValidationResult(false, "Number of cans must be between: " + Min + " - " + Max + ".");
        }
        else
        {
            return new ValidationResult(true, null);
        }
    }
}

Here is my main class.

public partial class MainWindow : Window
{
    public ObservableCollection<Drinks> SomeDrinks { get; private set; }

    public MainWindow()
    {
        InitializeComponent();

        SomeDrinks = new ObservableCollection<Drinks>();

        SomeDrinks.Add(new Drinks("Soda", "Pepsi", 5));         
        SomeDrinks.Add(new Drinks("Tea", "Lemon", 3));
        SomeDrinks.Add(new Drinks("Caffinated", "Coffee", 0));
        SomeDrinks.Add(new Drinks("Other", "Water", 0));

        DrinksListBox.ItemsSource = SomeDrinks;
        DrinkTypeComboBox.ItemsSource = SomeDrinks;
    }

    private void CmdDeleteDrink_Clicked(object sender, RoutedEventArgs e)
    {
        Button cmd = (Button)sender;

        if (cmd.DataContext is Drinks deleteDrink)
        {
            SomeDrinks.Remove(deleteDrink);
        }
    }

    private void CmdAddDrink_Clicked(object sender, RoutedEventArgs e)
    {
        string typeSelection = ((Drinks)DrinkTypeComboBox.SelectedItem).Type;

        int canNum = Int32.Parse(NumberCansTextBox.Text);

        SomeDrinks.Add(new Drinks(typeSelection, DrinkNameTextBox.Text, canNum)
        {
            IsUserDefined = true
        });
    }
}

public class Drinks
{
    private string type;
    private string name;
    private int numCans;

    public Drinks(string type, string name, int numCans)
    {
        this.type = type;
        this.name = name;
        this.numCans = numCans;
    }

    public bool IsUserDefined { get; set; }

    public string Type
    {
        get { return type; }

        set
        {
            if (type != value)
            {
                type = value;
            }
        }
    }

    public string Name
    {
        get { return name; }

        set
        {
            if (name != value)
            {
                name = value;
            }
        }
    }

    public int NumberOfCans
    {
        get { return numCans; }

        set
        {
            if (numCans != value)
            {
                numCans = value;
            }
        }
    }
}

My XAML is here.

<Window x:Class="WpfApp1.MainWindow"
    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:WpfApp1"
    mc:Ignorable="d"
    Title="MainWindow" Height="450" Width="800">
<Window.Resources>
    <BooleanToVisibilityConverter x:Key="BoolToVis"/>

    <ControlTemplate x:Key="validationTemplate">
        <DockPanel>
            <TextBlock Foreground="Red" FontSize="20">!</TextBlock>
            <AdornedElementPlaceholder/>
        </DockPanel>
    </ControlTemplate>

    <Style x:Key="textStyleTextBox" TargetType="TextBox">
        <Setter Property="Foreground" Value="#333333" />
        <Setter Property="MaxLength" Value="40" />
        <Setter Property="Width" Value="392" />
        <Style.Triggers>
            <Trigger Property="Validation.HasError" Value="true">
                <Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors)[0].ErrorContent}"/>
            </Trigger>
        </Style.Triggers>
    </Style>
</Window.Resources>

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>

    <ListBox x:Name="DrinksListBox" HorizontalAlignment="Center" Height="325" Width="275" Margin="0,0,0,0" VerticalAlignment="Center" Grid.Column="0" ItemsSource="{Binding SomeDrinks}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Grid Margin="0,2">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                    <TextBlock Text="{Binding Type}" Width="80"  Margin="0,0,10,0" Grid.Column="0"/>
                    <TextBlock Text="{Binding Name}" Width="80"  Margin="0,0,10,0" Grid.Column="1" HorizontalAlignment="Left"/>
                    <TextBlock Text="{Binding NumberOfCans}" Width="80"  Margin="0,0,10,0" Grid.Column="2" HorizontalAlignment="Left"/>
                    <Button x:Name="DrinkDeleteButton" Content="Delete" Visibility="{Binding Path=IsUserDefined, Converter={StaticResource BoolToVis}}" Click="CmdDeleteDrink_Clicked" HorizontalAlignment="Left" Grid.Column="3"/>
                </Grid>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

    <TextBox x:Name="DrinkNameTextBox" Grid.Column="1" HorizontalAlignment="Left" Height="45" Margin="0,0,0,100" TextWrapping="Wrap" Text="Enter Drink Name" VerticalAlignment="Center" Width="240" FontSize="20" VerticalContentAlignment="Center"/>
    <TextBox x:Name="NumberCansTextBox" Style="{StaticResource textStyleTextBox}" Grid.Column="1" HorizontalAlignment="Left" Height="45" Margin="0,0,0,150" VerticalAlignment="Bottom" Width="240" FontSize="20" VerticalContentAlignment="Center">
        <TextBox.Text>
            <Binding Path="NumberOfCans" UpdateSourceTrigger="PropertyChanged">
                <Binding.ValidationRules>
                    <local:NumberCansValidationRule Min="0" Max="10"/>
                </Binding.ValidationRules>
            </Binding>
        </TextBox.Text>
    </TextBox>
    <ComboBox x:Name="DrinkTypeComboBox" Grid.Column="1" HorizontalAlignment="Left" Margin="0,47,0,0" VerticalAlignment="Top" Width="240" Height="45" ItemsSource="{Binding Drinks,  Mode=OneWay}" DisplayMemberPath="Type" FontSize="20"/>
    <Button x:Name="AddDrinkButton" Content="Add Drink" Grid.Column="1" HorizontalAlignment="Right" Margin="0,0,10,100" VerticalAlignment="Center" Width="100" Height="45" Click="CmdAddDrink_Clicked"/>
</Grid>

Answer 1

Firstly you need to add

<Window.Resources>
    <local:Drinks x:Key="Drink"/>
...
</Window.Resources>
...
<Binding Path="NumberOfCans" UpdateSourceTrigger="PropertyChanged"  Source="{StaticResource Drink}">
...

and constructor without parameters

public Drinks()
{
}