How to Open an Excel File in C#

How to open an Excel file in C#?

You need to have installed Microsoft Visual Studio Tools for Office (VSTO).

VSTO can be selected in the Visual Studio installer under Workloads > Web & Cloud > Office/SharePoint Development.

After that create a generic .NET project and add a reference to Microsoft.Office.Interop.Excel via 'Add Reference... > Assemblies' dialog.

Application excel = new Application();
Workbook wb = excel.Workbooks.Open(path);

Missing.Value is a special reflection struct for unnecessary parameters replacement

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In newer versions, the assembly reference required is called Microsoft Excel 16.0 Object Library. If you do not have the latest version installed you might have Microsoft Excel 15.0 Object Library, or an older version, but it is the same process to include.

Opening an Excel file in C# using Process.Start

Normally, Process.Start(@"C:\Users\username\Documents\newTest.xlsx"); would open your document in Excel.

However, you say in a comment that you are doing this from an Excel add-in which runs in the background. The solution needs to take this into account (the code sample assumes that you have a VSTO add-in, otherwise you need to adjust accordingly):

// make the running Excel instance visible
Globals.ThisAddIn.Application.Visible = true;

// open the workbook using Excel interop
Globals.ThisAddIn.Application.Workbooks.Open(fileName);

C# - Proper way to open and close an excel file programmatically

Semi pseudo-code:

using Excel = Microsoft.Office.Interop.Excel;

# declare the application object
Excel.Application xl = new Excel.Application();

# open a file
Excel.Workbook wb = xl.Workbooks.Open("some_file.xlsx");

# do stuff ....

# close the file
wb.Close();

# close the application and release resources
xl.Quit();

How to open an excel document using c#

If excel is set as the default viewer for xls files on the system you can open the file using Process class:

System.Diagnostics.Process.Start("myFile.xls");

Opening an excel file using asp.net C#

If you want users of your website to open an excel file that you've created on server, than you don't need to open it there - just send it to the user. Replace the last two lines of code with this:

string filePath = directory + "Employee_lwpc_Details.xls"; 
Response.ContentType = "Application/vnd.ms-excel"; 
Response.AppendHeader("content-disposition", 
"attachment; filename=" + "Employee_lwpc_Details.xls"); 
Response.TransmitFile(filePath); 
Response.End();

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