MainActivity 代码：

public class MainActivity : Activity
{
    TextView _dateDisplay;
    Button _dateSelectButton;

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);
        SetContentView(Resource.Layout.Main);

        _dateDisplay = FindViewById<TextView>(Resource.Id.date_display);
        _dateSelectButton = FindViewById<Button>(Resource.Id.date_select_button);
        _dateSelectButton.Click += DateSelect_OnClick;
    }

    void DateSelect_OnClick(object sender, EventArgs eventArgs)
    {
        DatePickerFragment frag = DatePickerFragment.NewInstance(delegate (DateTime time)
        {
            _dateDisplay.Text = time.ToLongDateString();
        });
        frag.Show(FragmentManager, DatePickerFragment.TAG);
    }
}

DatePickerFragment.cs 代码：

public class DatePickerFragment : DialogFragment, DatePickerDialog.IOnDateSetListener
{
    // TAG can be any string of your choice.
    public static readonly string TAG = "X:" + typeof(DatePickerFragment).Name.ToUpper();

    // Initialize this value to prevent NullReferenceExceptions.
    Action<DateTime> _dateSelectedHandler = delegate { };

    public static DatePickerFragment NewInstance(Action<DateTime> onDateSelected)
    {
        DatePickerFragment frag = new DatePickerFragment();
        frag._dateSelectedHandler = onDateSelected;
        return frag;
    }

    public override Dialog OnCreateDialog(Bundle savedInstanceState)
    {
        DateTime currently = DateTime.Now;
        DatePickerDialog dialog = new DatePickerDialog(Activity,
                                                       this,
                                                       currently.Year,
                                                       currently.Month - 1,
                                                       currently.Day);
        return dialog;
    }

    public void OnDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth)
    {
        // Note: monthOfYear is a value between 0 and 11, not 1 and 12!
        DateTime selectedDate = new DateTime(year, monthOfYear + 1, dayOfMonth);
        Log.Debug(TAG, selectedDate.ToLongDateString());
        _dateSelectedHandler(selectedDate);
    }
}

Main.axml 代码：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/top_padding">
    <TextView
        android:id="@+id/date_display"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:paddingTop="@dimen/top_padding"
        android:text="@string/selected_date_text"
        style="@android:style/TextAppearance.Large" />
    <Button
        android:id="@+id/date_select_button"
        android:paddingLeft="@dimen/left_padding"
        android:paddingRight="@dimen/right_padding"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/pick_date_text"
        android:layout_below="@id/date_display" />
</RelativeLayout>

实现结果：

 

 参考文献：

　　https://docs.microsoft.com/zh-cn/xamarin/android/user-interface/controls/pickers/date-picker