In this section, you will create a checkbox for selecting items, using the CheckBox widget. When the checkbox is pressed, a toast message will indicate the current state of the checkbox.

Open the Resources/layout/Main.axml file and add the CheckBox element (inside the LinearLayout):

<CheckBox android:id="@+id/checkbox"
        android:text="check it out" />

To do something when the state is changed, add the following code to the end of the OnCreate() method:

CheckBox checkbox = FindViewById<CheckBox>(Resource.Id.checkbox);

checkbox.Click += (o, e) => {
    if (checkbox.Checked)
        Toast.MakeText (this, "Selected", ToastLength.Short).Show ();
        Toast.MakeText (this, "Not selected", ToastLength.Short).Show ();

This captures the CheckBox element from the layout, then handles the Click event, which defines the action to be made when the checkbox is clicked. When clicked, the Checked property is called to check the new state of the check box. If it has been checked, then a Toast displays the message "Selected", otherwise it displays "Not selected". The CheckBox handles its own state changes, so you only need to query the current state.

Run it.

Tip: If you need to change the state yourself (such as when loading a saved CheckBoxPreference, use the Checked property setter or Toggle() method.

Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.