WPF绑定到TextBlock不会更新

Question

I have a ViewModel like so:

class CalculatorViewModel : INotifyPropertyChanged
{
    private string _currentNumber = "0";


    public string CurrentNumber
    {
        get
        {
            return _currentNumber;
        }
        set
        {
            _currentNumber = value;
            NotifyPropertyChanged("Updated current number.");
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void NotifyPropertyChanged(string info)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(info));
    }

    public Command ButtonPressedCommand => new Command(ButtonPressed);

    private void ButtonPressed(object obj)
    {
        var button = obj as Button;
        if (button != null)
        {
            CurrentNumber += button.Content.ToString();
        }
        else
        {
            throw new NullReferenceException("The object passed into the command cannot be casted to a button.");
        }
    }
}

I also have a view like so:

<Window x:Name="window_Calculator" x:Class="Calculator.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:Calculator"
        mc:Ignorable="d"
        Title="Calculator" Height="350" Width="281.091" ResizeMode="NoResize" WindowStartupLocation="CenterScreen">
    <Window.DataContext>
        <local:CalculatorViewModel />
    </Window.DataContext>
    <Grid>
        <TextBlock x:Name="textBlock" Margin="10,10,10,252" TextWrapping="Wrap" Text="{Binding CurrentNumber}" FontSize="29.333" MaxHeight="57" MaxWidth="235"/>
        <Button x:Name="button_7" Content="7" Margin="10,67,217,215" FontSize="18.667" MaxHeight="37" MaxWidth="46"  Command="{Binding ButtonPressedCommand}" CommandParameter="{Binding RelativeSource={RelativeSource Self}}"/>
        <Button x:Name="button_8" Content="8" Margin="61,67,166,215" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_9" Content="9" Margin="112,67,115,215" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_4" Content="4" Margin="10,109,217,173" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_5" Content="5" Margin="61,109,166,173" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_6" Content="6" Margin="112,109,115,173" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_1" Content="1" Margin="10,151,217,131" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_2" Content="2" Margin="61,151,166,131" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_3" Content="3" Margin="112,151,115,131" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_plus" Content="+" Margin="217,67,10,215" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_minus" Content="-" Margin="217,109,10,173" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_multiply" Content="*" Margin="217,151,10,131" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_divide" Content="\" Margin="217,193,10,89" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
        <Button x:Name="button_equals" Content="=" Margin="217,262,10,10" FontSize="18.667" MaxHeight="37" MaxWidth="46"/>
    </Grid>
</Window>

The problem I've having is that when I click the '7' button, the CurrentNumber value when degugging updates like it should (ie it appends 7 to the string), however the textblock does not display the updated string even though I've bound it.

I've tried:

• Setting the Mode to TwoWay
• Setting the UpdateSourceTrigger to PropertyChanged
• One of the above
• None of the above

I believe I've followed the correct steps to implement INotifyExecption as property is being raised everytime the button is clicked and the setter is being called everything the command is called, I can't seem to find an answer anywhere else either.

Thanks for your help.

Answer 1

In the NotifyPropertyChanged() method you have to pass property name as parameter to have it work, currently you are passing some other text which is causing problem :

    set
    {
        _currentNumber = value;
        NotifyPropertyChanged("CurrentNumber");
    }

For reference see this tutorial