Question

这是我的XAML代码：

<Label x:Name="faveLabel" FontFamily="FontAwesome" 
   XAlign="Center" FontSize="23">
   <Label.Triggers>
      <DataTrigger TargetType="Label" Binding="{Binding Favorite}" Value="true">
         <Setter Property="TextColor" Value="Red"/>
      </DataTrigger>
      <DataTrigger TargetType="Label" Binding="{Binding Favorite}" Value="false">
         <Setter Property="TextColor" Value="Gray"/>
      </DataTrigger>
   </Label.Triggers>
</Label>

我想做的是将其更改为C＃

        var label = new Label ()
        {
            FontFamily = "FontAwesome",
            HorizontalTextAlignment = TextAlignment.Center,
            FontSize = 23,
        }

        var labelTrigger = new DataTrigger(label) 
        {
            Target


        }

我尝试在下面开始执行此操作，但在定义外部标签后不久我意识到我不知道如何定义触发器。任何人都可以就如何做到这一点给我建议吗？

Answer 1

我没有对此进行测试，但这应该会让你走上正轨：

// Trigger for Favorite = true
DataTrigger triggerTrue = new DataTrigger(typeof(Label));
triggerTrue.Value = true;
triggerTrue.Binding = new Binding() { Path = "Favorite" };
Setter setterTrue = new Setter();
setterTrue.Property = Label.TextColorProperty;
setterTrue.Value = Color.Red;
triggerTrue.Setters.Clear();
triggerTrue.Setters.Add(setterTrue);
label.Triggers.Add(triggerTrue);

// Trigger for Favorite = false    
DataTrigger triggerFalse = new DataTrigger(typeof(Label));
triggerFalse.Value = false;
triggerFalse.Binding = new Binding() { Path = "Favorite" };
Setter setterFalse = new Setter();
setterFalse.Property = Label.TextColorProperty;
setterFalse.Value = Color.Red;
triggerFalse.Setters.Clear();
triggerFalse.Setters.Add(setterFalse);
label.Triggers.Add(triggerFalse);

来源：https://social.msdn.microsoft.com/Forums/vstudio/en-US/797753f4-5db2-4852-a9fb-1ed989fe6413/add-datatrigger-programmatically?forum=wpf

Answer 2

带有触发器的ExtendedButton的示例，该触发器可根据IsEnabled属性更改按钮的样式：

public class ExtendedButton : Button
{
    public static readonly BindableProperty EnabledStyleProperty = 
            BindableProperty.Create(nameof(EnabledStyle),
            typeof(Style),
            typeof(ExtendedButton),
            default(Style),
            defaultBindingMode: BindingMode.TwoWay,
            propertyChanged: OnEnabledStyleChanged);

    public static readonly BindableProperty DisabledStyleProperty = 
            BindableProperty.Create(nameof(DisabledStyle),
            typeof(Style),
            typeof(ExtendedButton),
            default(Style),
            defaultBindingMode: BindingMode.TwoWay,
            propertyChanged: OnDisabledStyleChanged);

        public ExtendedButton()
        {
        }

        public Style EnabledStyle
        {
            get
            {
                return (Style)GetValue(EnabledStyleProperty);
            }

            set
            {
                SetValue(EnabledStyleProperty, value);

                var enabledStyleTrigger = GetEnabledStyleTrigger();
                this.Triggers.Clear();
                this.Triggers.Add(enabledStyleTrigger);
            }
        }

        public Style DisabledStyle
        {
            get
            {
                return (Style)GetValue(DisabledStyleProperty);
            }
            set
            {
                SetValue(DisabledStyleProperty, value);

                var disabledStyleTrigger = GetDisabledStyleTrigger();
                this.Triggers.Clear();
                this.Triggers.Add(disabledStyleTrigger);

            }
        }

        private static void OnEnabledStyleChanged(BindableObject bindable, object oldValue, object newValue)
        {
            var view = (ExtendedButton)bindable;
            view.EnabledStyle = (Style)newValue;
        }

        private static void OnDisabledStyleChanged(BindableObject bindable, object oldValue, object newValue)
        {
            var view = (ExtendedButton)bindable;
            view.DisabledStyle = (Style)newValue;
        }

        private Trigger GetDisabledStyleTrigger()
        {
            var disabledStyleTrigger = new Trigger(typeof(Button))
            {
                Property = Button.IsEnabledProperty,
                Value = true
            };
            var buttonDisabledSetter = new Setter
            {
                Property = Button.StyleProperty,
                Value = this.DisabledStyle
            };
            disabledStyleTrigger.Setters.Add(buttonDisabledSetter);
            return disabledStyleTrigger;
        }

        private Trigger GetEnabledStyleTrigger()
        {
            var enabledStyleTrigger = new Trigger(typeof(Button))
            {
                Property = Button.IsEnabledProperty,
                Value = true
            };
            var buttonEnabledSetter = new Setter
            {
                Property = Button.StyleProperty,
                Value = this.EnabledStyle
            };
            enabledStyleTrigger.Setters.Add(buttonEnabledSetter);
            return enabledStyleTrigger;
        }
    }
}

如何使用C＃而不是XAML向标签添加触发器？

2 个答案: