using Microsoft.Office.Interop.Excel;
 using System.Data.OleDb;

public DataSet seachExcel(string str) //参数为excel的路径
  {
    OleDbDataAdapter da = new OleDbDataAdapter();
    DataSet ds = new DataSet();
    DataTable dt = new DataTable();
    string NameTable = "";
    string ConText = "";
    try
    {
      //获取Excel路径
      FileInfo info = new FileInfo(str);
      //获取文件的扩展名
      string fileExt = info.Extension;
      //判断用哪种连接方式
      if (fileExt .ToLower() ==".xls")
      {
        ConText = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + str + ";Extended Properties='excel 8.0;hdr=no;IMEX=1';Persist Security Info=false";
      }
      else if (fileExt.ToLower() == ".xlsx")
      {
        ConText = "Provider=Microsoft.ACE.OLEDB.12.0; Data Source=" + str + ";Extended Properties='excel 12.0 Xml;hdr=no;IMEX=1';Persist Security Info=False";
      }
      //连接excel
      OleDbConnection conn = new OleDbConnection(ConText);
     //打开excel
      conn.Open();
      dt=conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables,null );
        if(dt!=null && dt.Rows .Count >0)
        {
          //获取sheet1表单的表名
          NameTable = dt.Rows[0]["TABLE_NAME"].ToString();
          //获取sheet2表单的表名
          //NameTable = dt.Rows[1]["TABLE_NAME"].ToString();
        }
        string sql = "select * from [" + NameTable + "]";
        da = new OleDbDataAdapter(sql, conn);
        try
        {
          da.Fill(ds,NameTable); //把数据填充到Dataset
        }  
        catch
        { }
        conn.Close();
    }
    catch
    {
    }
    return ds; //反回Dataset
}

string strDataPathPhy = "c://1.xls";
string strCon = " Provider = Microsoft.Jet.OLEDB.4.0 ; Data Source = " + strDataPathPhy + ";Extended Properties=Excel 8.0";
OleDbConnection myConn = new OleDbConnection(strCon);
string strCom = " SELECT * FROM [Sheet1$]";
myConn.Open();
OleDbDataAdapter myCommand = new OleDbDataAdapter(strCom, myConn);
DataTable dtData = new DataTable();
myCommand.Fill(dtData);
myConn.Close();