How can I add user-defined formulas to an instance of IWorkbook?

In order to make XlsIO recognize an unknown function, we need to register it as a custom add-in function. This ensures XlsIO can recognize and use it. We can achieve this by using the following code.

C#

// Define Function
IAddInFunctions unknownFunctions = workbook.AddInFunctions;
unknownFunctions.Add("TEST");
// Use Function
sheet.Range["A1"].Formula = "TEST(45)";

VB.NET

' Define Function
Dim unknownFunctions As IAddInFunctions = workbook.AddInFunctions
unknownFunctions.Add("TEST")
' Use Function
sheet.Range("A1").Formula = "TEST(45)"

Take a moment to peruse the documentation, where you can find basic worksheet data manipulation options along with features like Conditional Formatting, worksheet calculations through formulas, adding charts in worksheets or workbooks, organizing and analyzing data through tables and pivot tables, appending multiple records to a worksheet using template markers, and most importantly, PDF and image conversions, etc., with code examples.

Refer here to explore the rich set of Syncfusion Essential XlsIO features.

Note:

Starting with v16.2.0.x, if you reference Syncfusion assemblies from the trial setup or from the NuGet feed, include a license key in your projects. Refer to this link to learn about generating and registering a Syncfusion license key in your application to use the components without a trial message.

Conclusion

I hope you enjoyed learning about how you can add user-defined formulas to an instance of IWorkbook in XlsIO.

You can refer to our XlsIO’s feature tour page to learn about its other groundbreaking features. Explore our UG documentation and online demos to understand how to manipulate data in Excel documents.

If you are an existing user, you can access our latest components from the License and Downloads page. For new users, you can try our 30-day free trial to check out XlsIO and other Syncfusion components.

If you have any queries or require clarification, please let us know in the comments below or contact us through our support forums or feedback portal. We are always happy to assist you!