C# การใช้ DateTimePicker เพื่อใช้เปรียบเทียบวันเวลาแบบบ้านๆ

using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System;
using System.ComponentModel;

namespace TORServices.Forms
{
    public partial class refDate : UserControl
    {
        private System.Windows.Forms.DateTimePicker dateTimePicker1;
        private System.Windows.Forms.DateTimePicker dateTimePicker2;
        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.Label label1;
        private void InitializeComponent()
        {
            this.dateTimePicker1 = new System.Windows.Forms.DateTimePicker();
            this.dateTimePicker2 = new System.Windows.Forms.DateTimePicker();
            this.label1 = new System.Windows.Forms.Label();
            this.button1 = new System.Windows.Forms.Button();
            this.SuspendLayout();
            // 
            // dateTimePicker1
            // 
            this.dateTimePicker1.Location = new System.Drawing.Point(4, 4);
            this.dateTimePicker1.Name = "dateTimePicker1";
            this.dateTimePicker1.Size = new System.Drawing.Size(200, 20);
            this.dateTimePicker1.TabIndex = 0;
            this.dateTimePicker1.ValueChanged += new System.EventHandler(this.dateTimePicker1_ValueChanged);
            // 
            // dateTimePicker2
            // 
            this.dateTimePicker2.Location = new System.Drawing.Point(247, 4);
            this.dateTimePicker2.Name = "dateTimePicker2";
            this.dateTimePicker2.Size = new System.Drawing.Size(200, 20);
            this.dateTimePicker2.TabIndex = 1;
            this.dateTimePicker2.ValueChanged += new System.EventHandler(this.dateTimePicker1_ValueChanged);
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Font = new System.Drawing.Font("Microsoft Sans Serif", 14.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((byte)(222)));
            this.label1.Location = new System.Drawing.Point(214, 2);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(27, 24);
            this.label1.TabIndex = 3;
            this.label1.Text = "to";
            // 
            // button1
            // 
            this.button1.Location = new System.Drawing.Point(454, 0);
            this.button1.Name = "button1";
            this.button1.Text = "@";
            this.button1.Size = new System.Drawing.Size(36, 23);
            this.button1.TabIndex = 2;
            this.button1.UseVisualStyleBackColor = true;
            // 
            // refDate
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.BackColor = System.Drawing.Color.FromArgb(((int)(((byte)(255)))), ((int)(((byte)(224)))), ((int)(((byte)(192)))));
            this.Controls.Add(this.label1);
            this.Controls.Add(this.button1);
            this.Controls.Add(this.dateTimePicker2);
            this.Controls.Add(this.dateTimePicker1);
            this.Name = "refDate";
            this.Size = new System.Drawing.Size(497, 29);
            this.Resize += new System.EventHandler(this.refDate_Resize);
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        public refDate()
        {
            InitializeComponent();
        }
        private EventHandler onValueChanged;
        [
        Localizable(true),
        RefreshProperties(RefreshProperties.Repaint),
        ]
        public string CustomFormat
        {
            get
            {
                return dateTimePicker1.CustomFormat;
            }

            set
            {
                if (DateTimeFormat == DateTimePickerFormat.Custom)
                {
                    dateTimePicker1.CustomFormat = value;
                    dateTimePicker2.CustomFormat = value;
                }

            }
        }
        [System.ComponentModel.Browsable(true)]
        [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Always)]
        [System.ComponentModel.DefaultValue(DateTimePickerFormat.Long)]
        [System.ComponentModel.Category("Behavior")]
        [System.ComponentModel.Description("Open Dialog is dispalyed and on success the contents of the Cell is replaced with the new  path.")]
        public DateTimePickerFormat DateTimeFormat
        {
            get { return dateTimePicker1.Format; }
            set { dateTimePicker1.Format = value; dateTimePicker2.Format = value; }
        }
        public DateTime DateStart
        {
            get { return dateTimePicker1.Value; }
            set { dateTimePicker1.Value = value;  }
        }
        public DateTime DateFinal
        {
            get { return dateTimePicker2.Value; }
            set { dateTimePicker2.Value = value;  }
        }
        public event EventHandler ButtonRefreshClick
        {
            add
            {
                button1.Click += value;
            }
            remove
            {
                button1.Click -= value;
            }
        }
        public event EventHandler ValueChanged
        {
            add
            {
                onValueChanged += value;
            }
            remove
            {
                onValueChanged -= value;
            }
        }
        protected virtual void OnValueChanged(EventArgs eventargs)
        {
            if (onValueChanged != null)
            {
                onValueChanged(this, eventargs);
            }
        }
        private void refDate_Resize(object sender, EventArgs e)
        {
            this.Size = new Size(497, 29);
        }

        private void dateTimePicker1_ValueChanged(object sender, EventArgs e)
        {
            if (onValueChanged != null)
            {
                onValueChanged(this, e);
            }
        }
    }
}

private void refDate1_ValueChanged(object sender, EventArgs e)
        {
            //Preview by Date
this.aLS_F_717TableAdapter.FillByDate(this.bA_210S_1_2556DataSet.ALS_F_717,refDate1.DateStart,refDate1.DateFinal);
        }

        private void refDate1_ButtonRefreshClick(object sender, EventArgs e)
        {
//Preview All Data
            this.aLS_F_717TableAdapter.Fill(this.bA_210S_1_2556DataSet.ALS_F_717);
        }