How to write some data to excel file(.xlsx)

Try this code

Microsoft.Office.Interop.Excel.Application oXL;
Microsoft.Office.Interop.Excel._Workbook oWB;
Microsoft.Office.Interop.Excel._Worksheet oSheet;
Microsoft.Office.Interop.Excel.Range oRng;
object misvalue = System.Reflection.Missing.Value;
try
{
    //Start Excel and get Application object.
    oXL = new Microsoft.Office.Interop.Excel.Application();
    oXL.Visible = true;

    //Get a new workbook.
    oWB = (Microsoft.Office.Interop.Excel._Workbook)(oXL.Workbooks.Add(""));
    oSheet = (Microsoft.Office.Interop.Excel._Worksheet)oWB.ActiveSheet;

    //Add table headers going cell by cell.
    oSheet.Cells[1, 1] = "First Name";
    oSheet.Cells[1, 2] = "Last Name";
    oSheet.Cells[1, 3] = "Full Name";
    oSheet.Cells[1, 4] = "Salary";

    //Format A1:D1 as bold, vertical alignment = center.
    oSheet.get_Range("A1", "D1").Font.Bold = true;
    oSheet.get_Range("A1", "D1").VerticalAlignment =
        Microsoft.Office.Interop.Excel.XlVAlign.xlVAlignCenter;

    // Create an array to multiple values at once.
    string[,] saNames = new string[5, 2];

    saNames[0, 0] = "John";
    saNames[0, 1] = "Smith";
    saNames[1, 0] = "Tom";

    saNames[4, 1] = "Johnson";

    //Fill A2:B6 with an array of values (First and Last Names).
    oSheet.get_Range("A2", "B6").Value2 = saNames;

    //Fill C2:C6 with a relative formula (=A2 & " " & B2).
    oRng = oSheet.get_Range("C2", "C6");
    oRng.Formula = "=A2 & \" \" & B2";

    //Fill D2:D6 with a formula(=RAND()*100000) and apply format.
    oRng = oSheet.get_Range("D2", "D6");
    oRng.Formula = "=RAND()*100000";
    oRng.NumberFormat = "$0.00";

    //AutoFit columns A:D.
    oRng = oSheet.get_Range("A1", "D1");
    oRng.EntireColumn.AutoFit();

    oXL.Visible = false;
    oXL.UserControl = false;
    oWB.SaveAs("c:\\test\\test505.xls", Microsoft.Office.Interop.Excel.XlFileFormat.xlWorkbookDefault, Type.Missing, Type.Missing,
        false, false, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlNoChange,
        Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

    oWB.Close();
    oXL.Quit();

    //...