MVVM 中继命令在 Silverlight NumericUpDown 更改值之前触发

发布于 2024-10-05 02:35:42 字数 898 浏览 0 评论 0原文

如果您有绑定到 MVVM 属性和 RelayCommand 触发器集（任何事件）的 Silverlight 工具包 NumericUpDown 控件，则在 NumericUpDown 更改 MVVM 属性值之前调用该命令。这意味着，您不能在方法/操作/命令中使用新的（更改的）值...

XAML：

<inputToolkit:NumericUpDown x:Name="testNum" Value="{Binding RegisterForm, Mode=TwoWay}">
<i:Interaction.Triggers>
  <i:EventTrigger EventName="ValueChanged">
    <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding DoSomethingCommand}"/>
  </i:EventTrigger>
</i:Interaction.Triggers>
</inputToolkit:NumericUpDown>

MVVM (C#)：

DoSomethingCommand = new RelayCommand(() =>
            {
                OtherRegisterForm = RegisterForm;
            });

在这种情况下，如果您的 v 值为 0 并且在 NumericUpDown 控件中输入新值 123它会在 MVVM 属性上的“RaisePropertyChange”事件之前触发“DoSomethingCommand”。 “OtherRegisterForm”将是 0 而不是 123。

有没有办法让它工作？

原文

If you have a Silverlight Toolkit NumericUpDown control binded to a MVVM property and a RelayCommand trigger set (any event), the command is called before NumericUpDown changes MVVM property value. This means, you can not use the new (changed) value with you method/action/command...

XAML:

<inputToolkit:NumericUpDown x:Name="testNum" Value="{Binding RegisterForm, Mode=TwoWay}">
<i:Interaction.Triggers>
  <i:EventTrigger EventName="ValueChanged">
    <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding DoSomethingCommand}"/>
  </i:EventTrigger>
</i:Interaction.Triggers>
</inputToolkit:NumericUpDown>

MVVM (C#):

DoSomethingCommand = new RelayCommand(() =>
            {
                OtherRegisterForm = RegisterForm;
            });

In this case, if you have v value 0 and you input a new value 123 in NumericUpDown control it triggers the "DoSomethingCommand" before "RaisePropertyChange" event on MVVM property.
"OtherRegisterForm" would be 0 and not 123.

Is there a way to make this work?

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烟酉 2024-10-12 02:35:43

哦，天哪，这并不容易，但你在这里：

xaml 部分：

<toolkit:NumericUpDown Value="{Binding SomeNumber}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="ValueChanged">
                <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding MyCommand}" PassEventArgsToCommand="True" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </toolkit:NumericUpDown>

和 cs 代码：

    public class MainViewModel : ViewModelBase
{

    public double SomeNumber { get; set; }

    public MainViewModel()
    {
        SomeNumber = 10;
        MyCommand = new RelayCommand<RoutedPropertyChangedEventArgs<double>>(myActionMethod);
    }

    public RelayCommand<RoutedPropertyChangedEventArgs<double>> MyCommand { get; set; }

    public void myActionMethod(RoutedPropertyChangedEventArgs<double> arg)
    {
        MessageBox.Show(arg.NewValue.ToString());
    }
}

希望有帮助，Arek

oh boy, wasn't easy but here u are :

xaml part :

<toolkit:NumericUpDown Value="{Binding SomeNumber}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="ValueChanged">
                <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding MyCommand}" PassEventArgsToCommand="True" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </toolkit:NumericUpDown>

and cs code :

    public class MainViewModel : ViewModelBase
{

    public double SomeNumber { get; set; }

    public MainViewModel()
    {
        SomeNumber = 10;
        MyCommand = new RelayCommand<RoutedPropertyChangedEventArgs<double>>(myActionMethod);
    }

    public RelayCommand<RoutedPropertyChangedEventArgs<double>> MyCommand { get; set; }

    public void myActionMethod(RoutedPropertyChangedEventArgs<double> arg)
    {
        MessageBox.Show(arg.NewValue.ToString());
    }
}

hope that helps, Arek

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