#353 – Binding a Three-State CheckBox to a Nullable Bool

Because a three-state CheckBox can take on any one of three different values, its current value can’t be represented by a simple bool.  A bool can only take on true and false values.

A three-state CheckBox can instead be bound to a nullable bool (represented by bool?), which can take on three different values.

  • true  (checked)
  • false  (not checked)
  • null  (indeterminate)

In the example below, we bind a CheckBox control’s IsChecked property to a nullable bool property.

        <CheckBox Content="Happy" IsChecked="{Binding IsHappy}" IsThreeState="True"/>

In the code-behind, we define the property and set the main window’s data context.

        // Nullable bool - can be true, false or null
        public bool? IsHappy { get; set; }

		public MainWindow()
            this.DataContext = this;

About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

2 Responses to #353 – Binding a Three-State CheckBox to a Nullable Bool

  1. Pingback: #852 – Setting a Three-State CheckBox to an Indeterminate Value | 2,000 Things You Should Know About WPF

  2. mehrad1362 says:

    Sean, when I see your photo on the side of the article I know I have found my answer already. : )

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