How to check an excel workbook is already open in C# win forms

Question

I am opening multiple excel files in my application. Some will be automatically open when the application starts whereas some are opening at the run time.

Now I want to get data from an excel file on a button click. But before opening it, I want to check that excel file is already open.

1. If it is open , I want to read from it directly.
2. if it is not open , I want to open it and read from it.

But in both the cases I don't want to close the file after reading.`

I am using this method to open excel file.

objExcel = new Excel.ApplicationClass();
objWorkbook = objExcel.Workbooks.Open(...);`

Please help I am new to C#.

Answer 1

if i understand corectly, you actually want to find whether some files are already open by this winform application, right?

if so, i think it should be fairly simple - just cache the opened workbook to some dictionary or so:

    static Dictionary<string, Workbook> _openedWorkBooks = new Dictionary<string, Workbook>();    
    public static Workbook GetWorkbook(string filePath)  {    
        Workbook wkb = null;    
        if (!(_openedWorkBooks.TryGetValue(filePath, out wkb)))    
        {
            // Open the file and store it into the dictionary    
        }

        return wkb;  
    }

    // remember to remove it when it's closed  
    public static CloseWorkbook()  
    {    // need to remove the corresponding key from the dictionary  
    }

also, you could use single instance of excel application too, and then all the opened workbook could be rerieved from App.Workbooks, however, it throws some exception sometimes (not sure why, but i did encounter before).

  var app = new Microsoft.Office.Interop.Excel.Application(); var bk1 = app.Workbooks.Open("c:\\temp\\myfile.xls"); var allOpenBks = app.Workbooks; 

Actually it's still worth to call IsFileLock method to check the file is already open by other apps, otherwise you could encounter some errors.

Answer 2

You can checkk, if you have Read-Write access:

        /// <summary>
    /// Check wether a file is locked
    /// </summary>
    /// <param name="file"></param>
    /// <returns></returns>
    public static bool IsFileLocked(FileInfo file)
    {
        FileStream stream = null;

        try
        {
            stream = file.Open(FileMode.Open, FileAccess.ReadWrite, FileShare.None);
        }
        catch (IOException)
        {
            //the file is unavailable because it is:
            //still being written to
            //or being processed by another thread
            //or does not exist (has already been processed)
            return true;
        }
        finally
        {
            if (stream != null)
                stream.Close();
        }

        //file is not locked
        return false;
    }

The Code is from some one else on StackOverflow.

Do .xlsx? If so, you can use for reading and writing Excel-Files OpenXML.