wpf RelayCommand CanExecute 行为
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RelayCommand CanExecute behavior
提问by Night Walker
I have following command:
我有以下命令：
<Button x:Name="bOpenConnection" Content="Start Production"
Grid.Row="0" Grid.Column="0"
Height="30" Width="120" Margin="10"
HorizontalAlignment="Left" VerticalAlignment="Top"
Command="{Binding Path=StartProductionCommand}"/>
StartProductionCommand = new RelayCommand(OpenConnection, CanStartProduction);
private bool CanStartProduction()
{
return LogContent != null && !_simulationObject.Connected;
}
CanStartProductionis checked only when I re-size the UI and not updated on the fly.
Any idea why it's not updated every time they change the values ?
CanStartProduction仅在我重新调整 UI 大小时才检查，而不是即时更新。知道为什么每次更改值时都不更新吗？
回答by Thomas Levesque
The CommandManagerhas no way of knowing that the command depends on LogContentand _simulationObject.Connected, so it can't reevaluate CanExecuteautomatically when these properties change.
在CommandManager没有知道该命令取决于方式LogContent和_simulationObject.Connected，因此它不能重新评估CanExecute时，自动将这些特性的变化。
You can explicitly request a reevaluation by calling CommandManager.InvalidateRequerySuggested. Note that it will reevaluate CanExecutefor allcommands; if you want to refresh only one, you need to raise the CanExecuteChangedevent on the command itself by calling StartProductionCommand.RaiseCanExecuteChanged.
您可以通过调用显式请求重新评估CommandManager.InvalidateRequerySuggested。请注意，它会重新评估CanExecute了所有的命令; 如果只想刷新一个，则需要CanExecuteChanged通过调用StartProductionCommand.RaiseCanExecuteChanged.
回答by Boas Enkler
You can call RaiseCanExecuteChanged in the For example PropertyChanged Eventhandler.
您可以在例如 PropertyChanged 事件处理程序中调用 RaiseCanExecuteChanged。
Command states are not refreshed very often.
命令状态不会经常刷新。
Sometime ago I read a good article about it. I will post it later on.
前段时间我读了一篇关于它的好文章。稍后我会发布它。
see also Refresh WPF Command
另请参阅刷新 WPF 命令
