当绑定到viewModel属性时
我有一个带有 3 个依赖属性的简单 UserControl。日、月和年。
public static readonly DependencyProperty DayProperty = DependencyProperty.Register("Day", typeof(int), typeof(BoardPanel), new FrameworkPropertyMetadata(0));
public int Day
{
get { return (int)GetValue(DayProperty); }
set { SetValue(DayProperty, value); }
}
public static readonly DependencyProperty MonthProperty = DependencyProperty.Register("Month", typeof(int), typeof(BoardPanel), new FrameworkPropertyMetadata(0));
public int Month
{
get { return (int)GetValue(MonthProperty); }
set { SetValue(MonthProperty, value); }
}
public static readonly DependencyProperty YearProperty = DependencyProperty.Register("Year", typeof(int), typeof(BoardPanel), new FrameworkPropertyMetadata(0));
public int Year
{
get { return (int)GetValue(YearProperty); }
set { SetValue(YearProperty, value); }
}
和另一个字符串属性 DayOfWeek。
public string DayOfWeek
{
get { return new DateTime(Year, Month, Day).DayOfWeek.ToString(); }
}
Day 和 DayOfWeek 属性绑定到 XAML 中的两个文本框。
当使用此用户控件并手动设置所有值时，一切正常。
<c:DatePanel Day="1" Month="4" Year="2022"/>
绑定到我的 ViewModel 中的属性时，它会抛出异常并显示月份和年份为 0。
<c:DatePanel Day="2" Month="{Binding Month}" Year="{Binding Year}"/>
System.ArgumentOutOfRangeException：“年、月和日参数描述了无法表示的日期时间。”
我对这个主题很陌生，但我假设在控件初始化时绑定尚未解析还是什么？
你会如何正确地做到这一点？
I have a simple UserControl with 3 Dependency Properties. Day, Month and Year.
public static readonly DependencyProperty DayProperty = DependencyProperty.Register("Day", typeof(int), typeof(BoardPanel), new FrameworkPropertyMetadata(0));
public int Day
{
get { return (int)GetValue(DayProperty); }
set { SetValue(DayProperty, value); }
}
public static readonly DependencyProperty MonthProperty = DependencyProperty.Register("Month", typeof(int), typeof(BoardPanel), new FrameworkPropertyMetadata(0));
public int Month
{
get { return (int)GetValue(MonthProperty); }
set { SetValue(MonthProperty, value); }
}
public static readonly DependencyProperty YearProperty = DependencyProperty.Register("Year", typeof(int), typeof(BoardPanel), new FrameworkPropertyMetadata(0));
public int Year
{
get { return (int)GetValue(YearProperty); }
set { SetValue(YearProperty, value); }
}
and another string Property DayOfWeek.
public string DayOfWeek
{
get { return new DateTime(Year, Month, Day).DayOfWeek.ToString(); }
}
The Day and DayOfWeek Properties are bound to two Textboxes in XAML.
When using this UserControl and setting all values manually everything works fine.
<c:DatePanel Day="1" Month="4" Year="2022"/>
When binding these to Properties from my ViewModel however it throws an exeption and shows that Month and Year are 0.
<c:DatePanel Day="2" Month="{Binding Month}" Year="{Binding Year}"/>
System.ArgumentOutOfRangeException: "Year, Month, and Day parameters describe an un-representable DateTime."
I'm quite new to this topic but I'd assume that the binding is not resolved yet at the time the control gets initialized or something?
How would you do this correctly?
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显然，您的绑定行不通。
原因是您已明确设置
usercontrol的dataContext本身，从而有效防止其继承dataContext具有其特性。Don't do this:
You should also raise a property changed event for the
DayOfWeekproperty whenever theDay,MonthorYear< /code>属性已设置，但我在代码中没有看到propertyChangedCallback。Apparently your bindings don't work.
The reason is that you have explicitly set the
DataContextof theUserControlto itself which effectively prevents it from inheriting theDataContextfrom its parent element and bind to the properties of it.Don't do this:
You should also raise a property changed event for the
DayOfWeekproperty whenever theDay,MonthorYearproperty is set but I see noPropertyChangedCallbackin your code.