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

namespace DataSetHasChanges
{
	public class frmTest : Form
	{
		private DataSet _dataSet;
		private BindingSource _bs;
		private MyControl _myControl;
		private TextBox _textBox;
		

		public frmTest()
		{
			this.InitializeComponent();
			this.FillDataSet();
			this._dataSet.AcceptChanges();

			// если включить привязку к usercontrol-у то датасет начнет фиксировать изменения
			// ПОЧЕМУ???????????			
			// this._myControl.DataBindings.Add(new Binding("Value", this._bs, "col1", true, DataSourceUpdateMode.OnValidation, "(null)"));
			this._textBox.DataBindings.Add(new Binding("Text", this._bs, "col1", true, DataSourceUpdateMode.OnValidation, "(null)"));
		}

		void frmTest_FormClosing(object sender, FormClosingEventArgs e)
		{
			this._bs.EndEdit();
			if (this._dataSet.HasChanges())
			{
				MessageBox.Show("Data set has changes... (do you want to save changes?)");
			}
		}

		private void FillDataSet()
		{
			for (int i = 1; i < 5; i++)
			{
				DataRow r = this._dataSet.Tables[0].NewRow();
				r["col1"] = "Item " + i.ToString();
				this._dataSet.Tables[0].Rows.Add(r);
			}
		}
		private void InitializeComponent()
		{
			// dataset
			this._dataSet = new DataSet();
			DataTable t1 = new DataTable("t1");
			t1.Columns.Add("col1", typeof(string));
			this._dataSet.Tables.Add(t1);

			// bindingsource
			this._bs = new BindingSource();
			this._bs.DataSource = this._dataSet;
			this._bs.DataMember = this._dataSet.Tables[0].TableName;
			
			// usercontrol
			_myControl = new MyControl();
			this.Controls.Add(_myControl);

			// textbox
			_textBox = new TextBox();
			_textBox.Location = new Point(100, 0);
			this.Controls.Add(_textBox);
			// form
			this.FormClosing += new FormClosingEventHandler(frmTest_FormClosing);
		}
	}

	[DefaultBindingProperty("Value")]
	[DefaultProperty("Value")]
	public class MyControl : UserControl
	{
		private TextBox _textBox;

		public MyControl()
		{
			this.InitializeComponent();
		}

		private void InitializeComponent()
		{
			this._textBox = new TextBox();
			this._textBox.BackColor = Color.LightGray;
			this.Controls.Add(this._textBox);
			this.Size = new Size(100, 30);
		}

		public string Value
		{
			get { return this._textBox.Text; }
			set
			{
				if (this._textBox.Text != value)
					this._textBox.Text = value;
			}
		}
	}

	static class Program
	{
		[STAThread]
		static void Main()
		{
			Application.EnableVisualStyles();
			Application.SetCompatibleTextRenderingDefault(false);
			Application.Run(new frmTest());
		}
	}


}

	[DefaultBindingProperty("Value")]
	[DefaultProperty("Value")]
	public class MyControl : UserControl
	{
		// вот это событие надо обьявить
		public event EventHandler ValueChanged;

		private TextBox _textBox;

		public MyControl()
		{
			this.InitializeComponent();
		}

		private void InitializeComponent()
		{
			this._textBox = new TextBox();
			this._textBox.BackColor = Color.LightGray;
			// вот здесь подписаться на изменение текста
			this._textBox.TextChanged += new EventHandler(_textBox_TextChanged);
			this.Controls.Add(this._textBox);
			this.Size = new Size(100, 30);
		}

		// и вот здесь вызывать ValueChanged
		void _textBox_TextChanged(object sender, EventArgs e)
		{
			if (this.ValueChanged != null)
				this.ValueChanged(this, e);
		}

		public string Value
		{
			get { return this._textBox.Text; }
			set
			{
				if (this._textBox.Text != value)
					this._textBox.Text = value;
			}
		}
	}