在 WPF DataTrigger 值中绑定

Binding in WPF DataTrigger value

提问by Tanuj Wadhwa

Well, this may be an easy question but I am not able to find a solution for this.

好吧，这可能是一个简单的问题，但我无法找到解决方案。

I have a DataTriggeras

我有一个DataTrigger为

<DataTrigger Binding="{Binding Quantity}" Value="0">

Now I want to bind Valueto a variable myVariable. So if the value of myVariablechanges, the Valueproperty of the DataTrigger changes too.

现在我想绑定Value到一个变量myVariable。因此，如果值发生myVariable变化，ValueDataTrigger的属性也会发生变化。

I have tried setting Binding but it I guess its not possible to set it. Is there any other method by which I can set this Value dynamically.

我试过设置绑定，但我想它不可能设置它。有没有其他方法可以动态设置这个值。

EDIT : I tried creating a data trigger of my own. But I am still not able to get things working.

编辑：我尝试创建自己的数据触发器。但我仍然无法让事情发挥作用。

This is the code :

这是代码：

DataTrigger d = new DataTrigger();
d.Binding = new Binding("Quantity");
d.Value = 1;
Setter s = new Setter(BackgroundProperty, Brushes.Red);
d.Setters.Add(s);

Style st = new Style(typeof(DataGridRow));
st.Triggers.Add(d);
this.Resources.Add(this.Resources.Count, st);

I want to use the above code in place of following xaml

我想用上面的代码代替下面的 xaml

<Page.Resources>
    <Style TargetType="DataGridRow">
        <Style.Triggers>
            <DataTrigger Binding="{Binding Quantity}" Value="1">
                <Setter Property="Background" Value="Red" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Page.Resources>

Thanks.

谢谢。

采纳答案by Colin

To my understanding of your problem, you are trying to find a way to set the Valueof your DataTriggeraccording to the value of one of the properties of your view model. So here I have a solution.

要我对你的问题的理解，你正在努力寻找一种方法来设置Value您DataTrigger根据您的视图模型的属性之一的值。所以在这里我有一个解决方案。

Here is the View Model

这是视图模型

public class ViewModel : INotifyPropertyChanged
{
    private string _text;
    private string _candidateValue;

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

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

    public event PropertyChangedEventHandler PropertyChanged;
}

And you need a IValueConverter in your binding of DataTrigger

并且您在 DataTrigger 的绑定中需要一个 IValueConverter

public class ValueConverter : DependencyObject, IValueConverter
{

    public static readonly DependencyProperty CandidateValueProperty = DependencyProperty.Register("CandidateValue", typeof(string), typeof(ValueConverter));

    public string CandidateValue
    {
        get { return (string)GetValue(CandidateValueProperty); }
        set { SetValue(CandidateValueProperty, value); }
    }

    public ValueConverter()
        : base()
    { 
    }

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (null != value)
        {
            if (value.ToString() == this.CandidateValue)
                return true;
        }
        return false;
    }

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

And the xaml is quite simple

而且 xaml 很简单

<TextBox x:Name="TextBox" Text="{Binding Text,UpdateSourceTrigger=PropertyChanged}">
    </TextBox>

You need to create your datatrigger in code behind.

您需要在后面的代码中创建数据触发器。

public MainWindow()
    {
        InitializeComponent();

        //The view model object
        ViewModel vm = new ViewModel();
        vm.CandidateValue = "1";
        this.DataContext = vm;

        //create data trigger object for TextBox
        DataTrigger d = new DataTrigger();

        //create binding object for data trigger
        Binding b = new Binding("Text");

        ValueConverter c = new ValueConverter();
        b.Converter = c;
        //create binding object for ValueConverter.CandidateValueProperty
        Binding convertBinding = new Binding("CandidateValue");
        convertBinding.Source = vm;
        BindingOperations.SetBinding(c, ValueConverter.CandidateValueProperty, convertBinding);

        d.Binding = b;
        d.Value = true;

        Setter s = new Setter(TextBox.ForegroundProperty, Brushes.Red);
        d.Setters.Add(s);

        Style st = new Style(typeof(TextBox));
        st.Triggers.Add(d);
        this.TextBox.Style = st;
    }

The trick here is that the ValueConverterhas a dependency property named CandidateValueProperty. And this property is bind to the CandidateValueof view model. So the foreground of the TextBox will be red when the input value equals to CandidateValue of view model.

这里的技巧是ValueConverter有一个名为 的依赖属性CandidateValueProperty。此属性绑定到CandidateValue视图模型。所以当输入值等于视图模型的CandidateValue时，TextBox的前景将是红色的。