public DataTable LerExcel(string arquivo)
{
string cnnString = String.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=""Excel 8.0;HDR=YES;""", arquivo);
using (OleDbConnection conn = new OleDbConnection(cnnString))
{
conn.Open();
string firstSheet = conn.GetSchema("Tables").Rows[0]["TABLE_NAME"].ToString();
string sql = String.Format("SELECT * FROM [{0}]", firstSheet);
using (OleDbDataAdapter da = new OleDbDataAdapter(sql, conn))