Null可能なDateTimePicker

NullableDataTimePicker.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Globalization;
using System.Threading;

namespace ClassLibrary1
{
	public partial class NullableDateTimePicker : DateTimePicker
	{
		private DateTimePickerFormat format;

		public new string CustomFormat { get; set; }

		[Browsable(true)]
		[DefaultValue(DateTimePickerFormat.Long), TypeConverter(typeof(Enum))]
		public new DateTimePickerFormat Format
		{
			get
			{
				return this.format;
			}
			set
			{
				this.format = value;
				SetFormat();
				OnFormatChanged(EventArgs.Empty);
			}
		}

		private string formatAsString;
		private string FormatAsString
		{
			get
			{
				return formatAsString;
			}
			set
			{
				formatAsString = value;
				base.CustomFormat = value;
			}
		}

		private Boolean isNull;
		public new DateTime? Value
		{
			get
			{
				if (isNull) return null;

				return base.Value;
			}
			set
			{
				if (value == null || !value.HasValue)
				{
					SetToNullValue();
				}
				else
				{
					SetToDateTimeValue();
					base.Value = value.Value;
				}
			}
		}

		private void SetToNullValue()
		{
			this.isNull = true;
			base.CustomFormat = String.IsNullOrEmpty(this.NullValue) ? " " : "'" + this.NullValue + "'";
		}

		private void SetToDateTimeValue()
		{
			if (this.isNull)
			{
				SetFormat();
				this.isNull = false;
				base.OnValueChanged(new EventArgs());
			}
		}

		[Browsable(true)]
		[Category("Behavior")]
		[Description("�l��null�̂Ƃ��ɕ\������l��ݒ肵�܂��B")]
		[DefaultValue("          ")]
		public string NullValue { get; set; }

		private void SetFormat()
		{
			var ci = Thread.CurrentThread.CurrentCulture;
			var dateTimeFormat = ci.DateTimeFormat;
			switch (this.format)
			{
				case DateTimePickerFormat.Long:
					this.FormatAsString = dateTimeFormat.LongDatePattern;
					break;
				case DateTimePickerFormat.Short:
					this.FormatAsString = dateTimeFormat.ShortDatePattern;
					break;
				case DateTimePickerFormat.Time:
					this.FormatAsString = dateTimeFormat.ShortTimePattern;
					break;
				case DateTimePickerFormat.Custom:
					this.FormatAsString = this.CustomFormat;
					break;
			}
		}

		protected override void OnCloseUp(EventArgs eventargs)
		{
			if (Control.MouseButtons == System.Windows.Forms.MouseButtons.None && this.isNull)
			{
				SetToDateTimeValue();
				this.isNull = false;
			}
			base.OnCloseUp(eventargs);
		}

		protected override void OnKeyUp(KeyEventArgs e)
		{
			if (e.KeyCode == Keys.Delete)
			{
				this.Value = null;
				OnValueChanged(EventArgs.Empty);
			}
			base.OnKeyUp(e);
		}

		public NullableDateTimePicker() : base()
		{
			InitializeComponent();

			base.Format = DateTimePickerFormat.Custom;
			this.Format = DateTimePickerFormat.Custom;
		}
	}
}