C# – Cannot open Excel file in C#

cexcel-interop

I have the following C# function in my project, which is supposed to open and return an existing Excel workbook object:

Application _excelApp;

// ...

private Workbook OpenXL(string path, string filename)
{
    try
    {
        if (_excelApp == null)
        {
            _excelApp = new Application();
        }

        Workbook workBook = _excelApp.Workbooks.Open(path + filename,   // Name
                                                     0,                 // Do not update links
                                                     true);             // Open read-only

        return workBook;
    }
    catch (Exception e)
    {
        _excelApp = null;
        throw new ArgumentException("Error opening " + path + filename, e);
    }
}

But when I run it with "C:\" and "scratch.xlsx", the Open() call throws the following error:

Microsoft Excel cannot access the file 'C:\scratch.xlsx'. There are several possible reasons:

• The file name or path does not exist.
• The file is being used by another program.
• The workbook you are trying to save has the same name as a currently open workbook.

The file and path does exist: I have copied the path from the error message and pasted it into a command window and the file loads up in Excel.
The file is not locked: Excel can open it fine but my program cannot, even straight after a reboot.
I am not trying to save it, I am trying to open it so the last option is irrelevant.

I am at a loss to understand why this simple piece of code is not working. Any suggestions would be hugely appreciated.

[edit]
I have now tried opening that file from my personal network drive (M:) and from a USB stick. All to no avail.

The application is actually a Windows service, running under the local system account and generating reports. It currently write CSV reports with no access problems whatsoever. I am now trying to get it to open an excel file as a template report and fill in various fields. It is when opening the Excel file that it fails. I am thinking that the administrator account option everyone is suggesting is a red herring since it can write CSV files wityh no problem.
[/edit]

— Alistair.

Best Answer

I found the following page:

http://social.msdn.microsoft.com/Forums/en-US/b81a3c4e-62db-488b-af06-44421818ef91/excel-2007-automation-on-top-of-a-windows-server-2008-x64

Where it says that...

it’s not supported to automate office products UI less. It seems that Windows Server 2008 and Excel 2007 enforce the given statement.

The questioner then describes exactly the situation I am in with a Windows Service that cannot open an Excel file, although the same code in a command-line program has no problem.

The response advises to create the following folder:

Windows 2008 Server x64: C:\Windows\SysWOW64\config\systemprofile\Desktop

Windows 2008 Server x86: C:\Windows\System32\config\systemprofile\Desktop

I have tried this and it worked a treat! Can anyone explain why it is needed and any downsides?

Thanks,

--- Alistair.

Related Solutions

C# – How to create an Excel (.XLS and .XLSX) file in C# without installing Microsoft Office

You can use a library called ExcelLibrary. It's a free, open source library posted on Google Code:

ExcelLibrary

This looks to be a port of the PHP ExcelWriter that you mentioned above. It will not write to the new .xlsx format yet, but they are working on adding that functionality in.

It's very simple, small and easy to use. Plus it has a DataSetHelper that lets you use DataSets and DataTables to easily work with Excel data.

ExcelLibrary seems to still only work for the older Excel format (.xls files), but may be adding support in the future for newer 2007/2010 formats.

You can also use EPPlus, which works only for Excel 2007/2010 format files (.xlsx files). There's also NPOI which works with both.

There are a few known bugs with each library as noted in the comments. In all, EPPlus seems to be the best choice as time goes on. It seems to be more actively updated and documented as well.

Also, as noted by @АртёмЦарионов below, EPPlus has support for Pivot Tables and ExcelLibrary may have some support (Pivot table issue in ExcelLibrary)

Here are a couple links for quick reference:
ExcelLibrary - GNU Lesser GPL
EPPlus - GNU (LGPL) - No longer maintained
EPPlus 5 - Polyform Noncommercial - Starting May 2020
NPOI - Apache License

Here some example code for ExcelLibrary:

Here is an example taking data from a database and creating a workbook from it. Note that the ExcelLibrary code is the single line at the bottom:

//Create the data set and table
DataSet ds = new DataSet("New_DataSet");
DataTable dt = new DataTable("New_DataTable");

//Set the locale for each
ds.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;
dt.Locale = System.Threading.Thread.CurrentThread.CurrentCulture;

//Open a DB connection (in this example with OleDB)
OleDbConnection con = new OleDbConnection(dbConnectionString);
con.Open();

//Create a query and fill the data table with the data from the DB
string sql = "SELECT Whatever FROM MyDBTable;";
OleDbCommand cmd = new OleDbCommand(sql, con);
OleDbDataAdapter adptr = new OleDbDataAdapter();

adptr.SelectCommand = cmd;
adptr.Fill(dt);
con.Close();

//Add the table to the data set
ds.Tables.Add(dt);

//Here's the easy part. Create the Excel worksheet from the data set
ExcelLibrary.DataSetHelper.CreateWorkbook("MyExcelFile.xls", ds);

Creating the Excel file is as easy as that. You can also manually create Excel files, but the above functionality is what really impressed me.

C# – The located assembly’s manifest definition does not match the assembly reference

The .NET Assembly loader:

is unable to find 1.2.0.203
but did find a 1.2.0.200

This assembly does not match what was requested and therefore you get this error.

In simple words, it can't find the assembly that was referenced. Make sure it can find the right assembly by putting it in the GAC or in the application path. Also see https://docs.microsoft.com/archive/blogs/junfeng/the-located-assemblys-manifest-definition-with-name-xxx-dll-does-not-match-the-assembly-reference.

Best Answer

Related Solutions

C# – How to create an Excel (.XLS and .XLSX) file in C# without installing Microsoft Office

C# – The located assembly’s manifest definition does not match the assembly reference

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