CODEWITHSUNDEEP
.netwpfdata-bindingivalueconverter
Rich
Rich

Reputation: 36836

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

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.

Upvotes: 55

Views: 84040

Answers (7)

Michael Murphy
Michael Murphy

Reputation: 1981

Using Caliburn.Micro, I have the following code that works for my simple use case and may work for others.

In my View, I have a button that I want to be hidden unless one of my variables has a positive length string:

<Button x:Name="SelectBinaryFilePath" Content="Select" Visibility="{Binding CanSelectBinaryFile}" />

In my ViewModel I have the following property:

public Visibility CanSelectBinaryFile
{
    get
    {
        return String.IsNullOrEmpty(FileSystemPath) ? Visibility.Hidden : Visibility.Visible;
    }
}

Ensure to do a NotifyOfPropertyChange to ensure the CanSelectBinaryFile prop is updated.

Upvotes: 0

Steven Albright
Steven Albright

Reputation: 1

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: 

    Visibility="{Binding Path=Visible}"

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));
        }
    }

Upvotes: 0

Krzysztof Skowronek
Krzysztof Skowronek

Reputation: 2936

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

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:

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

Hope this helps :)

Upvotes: 1

Quartermeister
Quartermeister

Reputation: 59149

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

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);
}

Upvotes: 32

Drew Noakes
Drew Noakes

Reputation: 311255

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

[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:

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

Then use it in one or more bindings like this:

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

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

SILVERLIGHT USERS must 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.

Upvotes: 138

hkon
hkon

Reputation: 1045

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

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);
}

Upvotes: 4

cristobalito
cristobalito

Reputation: 4282

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

<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.

Upvotes: 8

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