Create an Excel app object and open the uploaded file:

Microsoft.Office.Interop.Excel.Application xlsApp = new ApplicationClass();

Workbook wb = xlsApp.Workbooks.Open(_filePath,Type.Missing,Type.Missing,
    Type.Missing,Type.Missing,Type.Missing,Type.Missing,
    Type.Missing,Type.Missing,Type.Missing,Type.Missing,
    Type.Missing,Type.Missing,Type.Missing,Type.Missing);

wb.Unprotect(TemplatePassword);
Save the upload file as a temporary file. Then close the uploaded file and open the temporary file as follows:

string tempFileName = _filePath.ToLower().Replace(".xls","_Temp.xls");
wb.Unprotect(TemplatePassword);
wb.SaveCopyAs(tempFileName);
Verify the data in the template again in the web application:
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ReadDataSource((Worksheet)wb.Worksheets[DataSourceSheet], 
    out branchID, out planDate, out startDate, out endDate, 
    out iChecked, out templatetype);

if(!(iChecked == 1))
{
    returnVal = "Please verify the data before upload to the server!";
    throw new Exception(returnVal);
}
if(templatetype.ToUpper() != _templatetype.ToUpper())
{
    returnVal = "The version is not corrected, 
    please verify the document and uploaded again";
    throw new Exception(returnVal);
}
……
private void ReadDataSource(Worksheet ws, out string branchID, 
    out string planDate, out DateTime startDate,out DateTime endDate, 
    out int iChecked, out string templatetype)
{
    string check = ws.get_Range("A1", System.Type.Missing).Text.ToString();
    branchID = ws.get_Range("A2", System.Type.Missing).Text.ToString();
    string sDate = ws.get_Range("A4", System.Type.Missing).Text.ToString();
    string eDate = ws.get_Range("A5", System.Type.Missing).Text.ToString();
    planDate = ws.get_Range("A6", System.Type.Missing).Text.ToString();
    templatetype = ws.get_Range("A7", System.Type.Missing).Text.ToString();
    startDate = DateTime.Parse(sDate);
    endDate = DateTime.Parse(eDate);
    try
    {
        iChecked = Convert.ToInt16(check);
    }
    catch
    {   
        iChecked = 0;
    }
 }