using System.IO;
・・・
private void Form1_Load(object sender, System.EventArgs e)
{
	//ツールバーのボタンを作成(ボタン３はセパレータ)
	ToolBarButton toolBarButton1 = new ToolBarButton();
	ToolBarButton toolBarButton2 = new ToolBarButton();
	ToolBarButton toolBarButton3 = new ToolBarButton();
	ToolBarButton toolBarButton4 = new ToolBarButton();

	//ボタンの文字を設定
	toolBarButton1.Text = "Open";
	toolBarButton2.Text = "Save";
	toolBarButton3.Style = ToolBarButtonStyle.Separator;
	toolBarButton4.Text = "Print";

	//ツールバーにボタンを追加
	toolBar1.Buttons.Add(toolBarButton1);
	toolBar1.Buttons.Add(toolBarButton2);
	toolBar1.Buttons.Add(toolBarButton3);
	toolBar1.Buttons.Add(toolBarButton4);
}

private void toolBar1_ButtonClick(object sender, System.Windows.Forms.ToolBarButtonClickEventArgs e)
{
	Stream myStream;

	switch(toolBar1.Buttons.IndexOf(e.Button))
	{
		case 0:
			OpenFileDialog openFileDialog1 = new OpenFileDialog();

			openFileDialog1.InitialDirectory = "c:\\" ;
			openFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*" ;
			openFileDialog1.FilterIndex = 2 ;
			openFileDialog1.RestoreDirectory = true ;

			if(openFileDialog1.ShowDialog() == DialogResult.OK)
			{
				if((myStream = openFileDialog1.OpenFile())!= null)
				{
					// Insert code to read the stream here.
					myStream.Close();
				}
			}

			//openFileDialog1.ShowDialog();
			// Insert code to open the file.
			break; 
		case 1:
			SaveFileDialog saveFileDialog1 = new SaveFileDialog();

			saveFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*"  ;
			saveFileDialog1.FilterIndex = 2 ;
			saveFileDialog1.RestoreDirectory = true ;

			if(saveFileDialog1.ShowDialog() == DialogResult.OK)
			{
				if((myStream = saveFileDialog1.OpenFile()) != null)
				{
					// Code to write the stream goes here.
					myStream.Close();
				}
			}
			//saveFileDialog1.ShowDialog();
			// Insert code to save the file.
			break; 
		case 3:
			//printDialog1.ShowDialog();
			// Insert code to print the file.    
			break; 
	}

}