Binding a Button's visibility to a bool value in ViewModel

Assuming AdvancedFormat is a bool, you need to declare and use a BooleanToVisibilityConverter:

<!-- In your resources section of the XAML --><BooleanToVisibilityConverter x:Key="BoolToVis" /><!-- In your Button declaration --><Button Height="50" Width="50" Style="{StaticResource MyButtonStyle}" Command="{Binding SmallDisp}" CommandParameter="{Binding}" Cursor="Hand" Visibility="{Binding Path=AdvancedFormat, Converter={StaticResource BoolToVis}}"/>

Note the added Converter={StaticResource BoolToVis}.

This is a very common pattern when working with MVVM. In theory you could do the conversion yourself on the ViewModel property (i.e. just make the property itself of type Visibility) though I would prefer not to do that, since now you are messing with the separation of concerns. An item's visbility should really be up to the View.

There's a third way that doesn't require a converter or a change to your view model: use a style:

<Style TargetType="Button">   <Setter Property="Visibility" Value="Collapsed"/>   <Style.Triggers>      <DataTrigger Binding="{Binding IsVisible}" Value="True">         <Setter Property="Visibility" Value="Visible"/>      </DataTrigger>   </Style.Triggers></Style>

I tend to prefer this technique because I use it in a lot of cases where what I'm binding to is not boolean - e.g. displaying an element only if its DataContext is not null, or implementing multi-state displays where different layouts appear based on the setting of an enum in the view model.

2 way conversion in c# from boolean to visibility

using System;using System.Windows;using System.Windows.Data;namespace FaceTheWall.converters{    class BooleanToVisibilityConverter : IValueConverter    {        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)        {            if (value is Boolean && (bool)value)            {                return Visibility.Visible;            }            return Visibility.Collapsed;        }        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)        {            if (value is Visibility && (Visibility)value == Visibility.Visible)            {                return true;            }            return false;        }    }}