C#

private void btnOpen_Click(object sender, System.EventArgs e)
{
try
{
Stream myStream;
OpenFileDialog openFileDialog1 = new OpenFileDialog();
// set up file dialog properties
openFileDialog1.InitialDirectory = "E:\\" ;
openFileDialog1.Filter = "txt files (*.txt)|*.txt|Allfiles(*.*)|*.*" ;
openFileDialog1.FilterIndex = 2 ;
openFileDialog1.RestoreDirectory = true ;
openFileDialog1.Multiselect = true;

if(openFileDialog1.ShowDialog() == DialogResult.OK)
{
if((myStream = openFileDialog1.OpenFile())!= null)
{
// Insert code to read the stream here.
// string strFileName = openFileDialog1.FileName;
DataSet ds = new DataSet();

foreach (string strFileName in openFileDialog1.FileNames)
{

string connStr = 
@"Driver={Microsoft Excel Driver (*.xls)};DBQ=" + strFileName;

string sql = "SELECT * FROM [Sheet1$]";
OdbcDataAdapter adapter = new OdbcDataAdapter(sql,connStr);
adapter.Fill(ds,"[Sheet1$]");

}
gridPorocila.DataMember = "[Sheet1$]";
gridPorocila.DataSource = ds.DefaultViewManager;

myStream.Close();
}
}

}
catch (Exception ex)
{
MessageBox.Show(ex.Message.ToString());
}

}