.net WPF BooleanToVisibilityConverter 在 false 时转换为隐藏而不是折叠？

WPF BooleanToVisibilityConverter that converts to Hidden instead of Collapsed when false?

提问by Rich

Is there a way to use the existing WPF BooleanToVisibilityConverter converter but have False values convert to Hidden instead of the default Collapsed, or should I just write my own? I'm on a project where it's tremendous overhead to do something simple like this (shared stuff goes into a separate solution, and the rebuild/checkin/merge process is an overgrown mutated behemoth of a process), so I'd prefer if I could just pass a parameter to the existing one than to jump through the hoops just mentioned.

有没有办法使用现有的 WPF BooleanToVisibilityConverter 转换器，但将 False 值转换为 Hidden 而不是默认的 Collapsed，还是我应该自己编写？我在一个项目中，做这样简单的事情会产生巨大的开销（共享的东西进入一个单独的解决方案，重建/签入/合并过程是一个过度生长的变异过程的庞然大物），所以我更喜欢如果我可以只将一个参数传递给现有的参数，而不是跳过刚才提到的箍。

采纳答案by Quartermeister

Unfortunately, it only converts to Visible or Collapsed, so you'll have to write your own. Here is the Convert method according to Reflector:

不幸的是，它只能转换为 Visible 或 Collapsed，因此您必须自己编写。这是根据 Reflector 的 Convert 方法：

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    bool flag = false;
    if (value is bool)
    {
        flag = (bool)value;
    }
    else if (value is bool?)
    {
        bool? nullable = (bool?)value;
        flag = nullable.HasValue ? nullable.Value : false;
    }
    return (flag ? Visibility.Visible : Visibility.Collapsed);
}

回答by Drew Noakes

I've found the simplest and best solution to be this:

我发现最简单和最好的解决方案是这样的：

[ValueConversion(typeof(bool), typeof(Visibility))]
public sealed class BoolToVisibilityConverter : IValueConverter
{
  public Visibility TrueValue { get; set; }
  public Visibility FalseValue { get; set; }

  public BoolToVisibilityConverter()
  {
    // set defaults
    TrueValue = Visibility.Visible;
    FalseValue = Visibility.Collapsed;
  }

  public object Convert(object value, Type targetType, 
      object parameter, CultureInfo culture)
  {
    if (!(value is bool))
      return null;
    return (bool)value ? TrueValue : FalseValue;    
  }

  public object ConvertBack(object value, Type targetType, 
      object parameter, CultureInfo culture)
  {
    if (Equals(value, TrueValue))
      return true;
    if (Equals(value, FalseValue))
      return false;
    return null;
  }
}

When using it, just configure a version that does exactly what you need it to in XAML like this:

使用它时，只需在 XAML 中配置一个完全符合您需要的版本，如下所示：

<Blah.Resources>
  <local:BoolToVisibilityConverter
         x:Key="BoolToHiddenConverter"
         TrueValue="Visible" FalseValue="Hidden" />
</Blah.Resources>

Then use it in one or more bindings like this:

然后在一个或多个绑定中使用它，如下所示：

<Foo Visibility="{Binding IsItFridayAlready, 
                          Converter={StaticResource BoolToHiddenConverter}}" />

This simple solution addresses hidden/collapsed preferences as well as reversing/negating the effect.

这个简单的解决方案解决了隐藏/折叠的偏好以及逆转/否定效果。

SILVERLIGHT USERSmust drop the [ValueConversion]declaration as that attribute is not part of the Silverlight framework. It's not strictly needed in WPF either, but is consistent with built-in converters.

SILVERLIGHT 用户必须删除[ValueConversion]声明，因为该属性不是 Silverlight 框架的一部分。在 WPF 中也不是严格需要的，但与内置转换器一致。

回答by cristobalito

Can you not just use a styleinstead of a converter? The code would be something like:

您不能只使用样式而不是转换器吗？代码类似于：

<Style x:Key="Triggers" TargetType="Button">
    <Style.Triggers>
    <Trigger Property="{Binding ...}" Value="false">
        <Setter Property = "Visibility" Value="Hidden"/>
    </Trigger>
    </Style.Triggers>
</Style>

You'll need to provide the property binding yourself to point to your bool property.

您需要提供绑定自己的属性以指向您的 bool 属性。

回答by hkon

I like to use the parameter for reversing the visibility logic: To reverse logic simply put: ConverterParameter=Reverse in your xaml code

我喜欢使用参数来反转可见性逻辑：要反转逻辑，只需在您的 xaml 代码中输入： ConverterParameter=Reverse

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    bool flag = false;
    if (value is bool)
    {
        flag = (bool)value;
    }

    var reverse = parameter as string;
    if(reverse != null && reverse == "Reverse")
        flag != flag;

    return (flag ? Visibility.Visible : Visibility.Collapsed);
}

回答by Krzysztof Skowronek

I wrote BoolToVisibilityConverte where you can pass invisible state in Parameter:

我写了 BoolToVisibilityConverte，您可以在其中传递参数中的不可见状态：

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    var boolValue = (bool) value;
    return boolValue ? Visibility.Visible : (parameter ?? Visibility.Hidden);
}

So you can bind like this:

所以你可以像这样绑定：

Visibility="{Binding SomeBool, Converter={StaticResource ResourceKey=BooleanToVisibilityConverter}, ConverterParameter={x:Static Visibility.Collapsed}}"

Hope this helps :)

希望这可以帮助 ：）

回答by Steven Albright

I had this issue crop up and my solution was probably very situational but I'll share it anyway. Due to my circumstance I was able to mimic the converter, without a converter, with a simple bit of code. I had visibility change only if a variable bound to a textbox made number box( through a Regex to ensure its a number) was not 0. The entire code for this is below however the WPF and first bit of C# is all you really need if you are going to change your boolean elsewhere in code. wpf:

我突然遇到了这个问题，我的解决方案可能非常特殊，但无论如何我都会分享。由于我的情况，我能够在没有转换器的情况下用一些简单的代码模拟转换器。仅当绑定到文本框的变量使数字框（通过正则表达式确保其数字）不为 0 时，我才能更改可见性。 整个代码如下，但是 WPF 和 C# 的第一位是你真正需要的，如果您将在代码中的其他地方更改您的布尔值。wpf：

    Visibility="{Binding Path=Visible}"

C#

C＃

    public class foo : INotifyPropertyChanged
    {
        private bool vis = false;
        public object Visible
        {
            get 
            { 
                if (vis == true) 
                { 
                    return Visibility.Visible; 
                } 
                else 
                { 
                    return Visibility.Hidden; 
                } 
            }
            set
            { 
                vis = (bool)value; 
                OnPropertyChanged(nameof(Visible)); 
            }
        }
        public int Value_b
        {
            get 
            { 
                return base_value;
            }
            set
            { 
                base_value = value; 
                OnPropertyChanged(nameof(Value_b));
                if (base_value == 0) 
                { 
                    Visible = false; 
                } 
                else 
                { 
                    Visible = true; 
                } 
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected virtual void OnPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new 
            PropertyChangedEventArgs(propertyName));
        }
    }