How to read excell cell value in C#?

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.NET

Hello All,

I am going to create application in .net for read Excell File.
I want to read more then 70 file at a time. every file contain one fix cell value and i want to read that cell.
I try and get this code from one site.
This code is working fine but i want to improve performance.

 public string readExcel()
{
            object _row = 3;
            object _column = 3;
            Microsoft.Office.Interop.Excel.Application excelApp = new Microsoft.Office.Interop.Excel.Application();
            excelApp.Visible = false;
            excelApp.ScreenUpdating = false;
            excelApp.DisplayAlerts = false;
            Microsoft.Office.Interop.Excel.Workbook excelWorkbook = excelApp.Workbooks.Open(@"D:\123.xlsx", 0, false, 5, "", "", false, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "", true, false, 0, true, false, false);
            Microsoft.Office.Interop.Excel.Sheets excelSheets = excelWorkbook.Worksheets;
            string currentSheet = "Sheet1";
            Microsoft.Office.Interop.Excel.Worksheet excelWorksheet = (Microsoft.Office.Interop.Excel.Worksheet)excelSheets.get_Item(currentSheet);
            Microsoft.Office.Interop.Excel.Range range = (Microsoft.Office.Interop.Excel.Range)excelWorksheet.UsedRange;
            string sValue = (range.Cells[_row, _column] as Microsoft.Office.Interop.Excel.Range).Value2.ToString();
            return sValue;
        } 

Please suggest me if you know how to improve performance?