Look it
string connstr ="Provider=Microsoft.Jet.Oledb.4.0;Data Source=C:\aaa.xls;Extended Properties=Excel 8.0"/>
OleDbConnection conn = new OleDbConnection(connstr);
string strSQL = "SELECT * FROM [Sheet$]";
OleDbCommand cmd = new OleDbCommand(strSQL, conn);
DataSet ds = new DataSet();
OleDbDataAdapter da = new OleDbDataAdapter(cmd);
da.Fill(ds);
GridView1.DataSource = ds;
GridView1.DataBind();