Excel Interop Code Examples

Writing code in C# with Excel Interop.

All code examples begin and end with

using Excel = Microsoft.Office.Interop.Excel;

Excel.Application app = new Excel.Application(); // Create Excel object instance
app.DisplayAlerts = false; // Don't display any Excel prompts
Excel.Workbook wb = app.Workbooks.Open(input_filepath); // Create workbook instance

[ANY CODE EXAMPLE]

wb.Save(); // Save workbook
wb.Close(); // Close workbook
app.Quit(); // Quit Excel application

Find if spreadsheet has sheets

int count = wb.Worksheets.Count;
if (count = 0)
{
    Console.WriteLine("Spreadsheet has no sheets");
}

Find and remove data connections

int count_conn = wb.Connections.Count;
if (count_conn > 0)
{
    for (int i = 1; i <= wb.Connections.Count; i++)
    {
        wb.Connections[i].Delete();
        i = i - 1;
    }
    count_conn = wb.Connections.Count;
    Console.WriteLine("--> Data connections detected and removed");
}

Remove author, subject and comments from file property details

if (wb.Author != "" || wb.Title != "" || wb.Subject != "" || wb.Keywords != "" || wb.Comments != "")
{
    Console.WriteLine("--> Removed file property details");
}

wb.Author = ""; // Remove author information
wb.Title = ""; // Remove title information
wb.Subject = ""; // Remove subject information
wb.Keywords = ""; // Remove keywords information
wb.Comments = ""; // Remove comments information

Find OLE objects

foreach (Excel.Worksheet sheet in wb.Sheets) // Loop over all sheets
{
    Excel.OLEObjects ole = (Excel.OLEObjects)sheet.OLEObjects(); // Find OLE objects in sheet
    int ole_count = ole.Count; // Count OLE objects in sheet
    if (count_conn > 0) // If any
    {
        Console.WriteLine($"--> {ole_count} OLE objects detected in sheet {sheet.Name}. Extract objects manually.");
    }
}

Convert to .xlsx Strict

wb.SaveAs(filepath, 61); // Save workbook as .xlsx Strict
wb.Save(); // You can delete this line, you do not need to save again

If the spreadsheet has embedded files (OLE objects), then the above code will not transform the namespaces of the embedded objects from Transitional to Strict namespaces. This should be considered a bug in Excel.