CODEWITHSUNDEEP
wpfmvvmdatatrigger
JohnChris
JohnChris

Reputation: 1360

How to get data binding to work with a simple MVVM structure

After getting the right answer, I thought I should update this to show the working code for people to have a future reference:

MainWindow.xaml

<Grid>
    <Grid.Resources>
        <local:ValueConverters x:Key="ValueConverters"></local:ValueConverters>
    </Grid.Resources>
    <TextBox Text="{Binding Text, UpdateSourceTrigger=PropertyChanged}">
        <TextBox.Style>
            <Style>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding Path=Text,Converter={StaticResource ValueConverters}}" Value="True">
                        <Setter Property="TextBox.Foreground" Value="Red"></Setter>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </TextBox.Style>
    </TextBox>
</Grid>

MainWindow.xaml.cs

public partial class MainWindow : MetroWindow
{
     private readonly DataBindingViewModel _vm = new DataBindingViewModel();

    public MainWindow()
    {
        InitializeComponent();
        DataContext = _vm;
    }
}

DataBindingViewModel.cs

public class DataBindingViewModel : INotifyPropertyChanged
{
    private string _text;

    public string Text
    {
        get
        {
            return this._text;
        }
        set
        {
            this._text = value;
            if (null != PropertyChanged)
            {
                this.PropertyChanged(this, new PropertyChangedEventArgs("Text"));
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

ValueConverters

public class ValueConverters : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (null != value)
        {
            if (value.ToString() == "1")
                return true;
        }
        return false;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        return null;
    }
}

The above now works:)

Upvotes: 0

Views: 87

Answers (2)

ASh
ASh

Reputation: 35730

you can change Foreground color for certain values without a converter. Use a trigger to compare Text value with a known string and change Foreground when they match

<TextBox Grid.Row="2" Text="{Binding Text, UpdateSourceTrigger=PropertyChanged}">
    <TextBox.Style>
        <Style>
            <Style.Triggers>
                <Trigger Property="TextBox.Text" Value="1">
                    <Setter Property="TextBox.Foreground" Value="Red"/>
                </Trigger>
            </Style.Triggers>
        </Style>
    </TextBox.Style>
</TextBox>

Upvotes: 2

Clemens
Clemens

Reputation: 128146

In your MainWindow's XAML the DataContext is set to an instance of ValueConverters:

<Window.DataContext>
    <local:ValueConverters/>
</Window.DataContext>

That doesn't seem to make sense. You should replace it with

<Window.DataContext>
    <local:DataBindingViewModel/>
</Window.DataContext>

You would not have to set the DataContext again in the MainWindow's constructor, but perhaps still assign the private field (for later use) like this:

private readonly DataBindingViewModel _vm;

public MainWindow()
{
    InitializeComponent();
    _vm = (DataBindingViewModel)DataContext;
}

Alternatively, do not set the DataContext at all in XAML, and create it in code behind like this:

private readonly DataBindingViewModel _vm = new DataBindingViewModel();

public MainWindow()
{
    InitializeComponent();
    DataContext = _vm;
}

Upvotes: 2

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