Save and delete Excel file saved using HttpPostedFileBase

问题

I am uploading an Excel file and extracting data from that and saving it into a database. I am using MVC4 .NET Framework. This is my code from class:

 public static void Upload(HttpPostedFileBase File)
        {
            NIKEntities1 obj = new NIKEntities1();
            MyApp = new Excel.Application();
            MyApp.Visible = false;
            string extension = System.IO.Path.GetExtension(File.FileName);

            string pic = "Excel" + extension;

            string path = System.IO.Path.Combine(System.Web.HttpContext.Current.Server.MapPath("~/Excel"), pic);

            File.SaveAs(path);


            MyBook = MyApp.Workbooks.Open(path);
            MySheet = (Excel.Worksheet)MyBook.Sheets[1]; // Explicit cast is not required here
            int lastRow = MySheet.Cells.SpecialCells(Excel.XlCellType.xlCellTypeLastCell).Row;
            List<Employee> EmpList = new List<Employee>();

            for (int index = 2; index <= lastRow; index++)
            {
                System.Array MyValues = (System.Array)MySheet.get_Range("A" +
                   index.ToString(), "B" + index.ToString()).Cells.Value;
                EmpList.Add(new Employee
                {
                    BatchID = MyValues.GetValue(1, 1).ToString(),
                    BatchName = MyValues.GetValue(1, 2).ToString()

                });
            }

            for (int i = 0; i < EmpList.Count; i++)
            {
                int x=obj.USP_InsertBatches(EmpList[i].BatchID, EmpList[i].BatchName);

            }    
        }
    }
    class Employee
    {
        public string BatchID;
        public string BatchName;
    }

This code is working perfectly the first time but next time it says that file is currently in use. So I thought of deleting the file at the end of code using the following line:

File.Delete(path);

But this line threw error:

HttpPostedFileBase does not contain definition for Delete

Also, if I don't write this line and try to execute code again it says that it can't save because a file exists with same name and could not be replaced because it is currently in use.

What should I do to get rid of this:

  (File.Delete()) Error

Any other way of accessing the Excel file which I am receiving without saving will also be very helpful because I have to just access the data one time.

回答1:

The File you use there is your variable that is the input parameter of your method. That parameter is of type HttpPostedFileBase and that type has no instance methods (nor static ones for that matter) that allow you to delete that File instance.

You are probably looking for the static Delete method on the File type that is in the System.IO namespace.

A quickfix would be to be explicit about which File you mean:

System.IO.File.Delete(path);

You might want to consider a different naming guideline for your variables though. In c# we tend to write variables starting with a lower case letter. Almost all types in the framework start with an Uppercase letter. Which makes it easier to distinguish the thing file and the type File.

Do notice that a file can only be deleted if it is closed by all processes and all file handles are cleared by the filesystem. In your case you have to make sure Excel closed the file and released it's handles. If you have the search indexer running or a rough virus scanner you might have to try a few times before giving up.

I normally use this code:

 // make sure here all Ole Automation servers (like Excel or Word)
 // have closed the file (so close the workbook, document etc)
 // we iterate a couple of times (10 in this case)
 for(int i=0; i< 10; i++) 
 {
     try 
     {
        System.IO.File.Delete(path);
        break;
     } catch (Exception exc) 
     {
         Trace.WriteLine("failed delete {0}", exc.Message);
         // let other threads do some work first
         // http://blogs.msmvps.com/peterritchie/2007/04/26/thread-sleep-is-a-sign-of-a-poorly-designed-program/
         Thread.Sleep(0);
     }
 }

回答2:

From what I can tell, you are opening Excel, reading the file but never closing the Excel.

Add:

MyApp.Workbooks.Close();
MyApp.Quit();

at the end of the Upload function. Even better, wrap whole code you got in

try{
  //here goes your current code
}
catch(Exception e)
{
 //manage exception
}
finally
{
MyApp.Workbooks.Close();
MyApp.Quit();
}

You initialize MyApp outside try catch block, then whatever happens close the file.

来源：https://stackoverflow.com/questions/32738029/save-and-delete-excel-file-saved-using-httppostedfilebase

标签

excel

asp.net-mvc-4

httppostedfilebase