how to open and read an excel file ?!!

If you don't want to use the Excel COM objects, you can use OleDb. It takes a little setup in your Excel document. Basically, you need to define "named objects" in Excel that are synonymous to tables in a database. The first row of the named object are the column headers. To set up a named object, first select the range of cells (your "table," with the first row being the column headers), then go to menu Insert->Names->Define. Name your object and press "Add." Now you have an object which can be read by ADO.NET.

Now for the C# (this example assumes I have an Excel file at C:\Book1.xls and a named object in this workbook called "MyObject"):

using System.Data;
using System.Data.OleDb;

...

OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Book1.xls;Extended Properties=Excel 8.0");
OleDbDataAdapter da = new OleDbDataAdapter("select * from MyObject", con);
DataTable dt = new DataTable();
da.Fill(dt);

Now you can save this data table into DB.

To transform the contents of excel into array:

Excel.Workbook theWorkbook = ExcelObj.Workbooks.Open(
        openFileDialog1.FileName, 0, true, 5,
         "", "", true, Excel.XlPlatform.xlWindows, "\t", false, false,
         0, true);
    Excel.Sheets sheets = theWorkbook.Worksheets;
    Excel.Worksheet worksheet = (Excel.Worksheet)sheets.get_Item(1);
    for (int i = 1; i <= 10; i++)
    {
    Excel.Range range = worksheet.get_Range("A"+i.ToString(), "J" + i.ToString());
    System.Array myvalues = (System.Array)range.Cells.Value;
    string[] strArray = ConvertToStringArray(myvalues);
    }

Now you can iterate through the array[].

Edit: Code formatted