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0	vb

 Public Sub RegisterCustomFunction(customFunctionName As String, customFunction As IFunction)

Note

title	Disabling Excel Calculation

Registering a formula allows ExcelWriter to calculate a function a certain way. However, once the workbook opens inside of Microsoft Excel, Excel will calculate the formula again with its own calculation engine. This means that if you registered a function name that does not exist in Excel, your formula will evaluate to #NAME? once Excel recalculates it. If you overwrote a formula with you own implementation, the formula will be recalculated using the implementation that is built into Excel. To keep Excel from re-calculating the formulas upon opening the workbook or upon changing values in the workbook, go to File -> Options -> Formulas. Under the "Calculation Options" header, there is an option called "Workbook Calculation". Please select the "Manual" option and uncheck the "Recalculate workbook before saving" checkbox. Now Excel will not re-calculate formulas. These settings will allow you to preserve the values that ExcelWriter calculated.

Example

Code Block

title	C#
language	c#

//Create an ExcelApplication object
ExcelApplication xla = new ExcelApplication();

//Open a workbook containing formulas
Workbook wb = xla.Open("FormulasWorkbook.xlsx); 

// Create an instance of the custom function implementation
IFunction myCustomFunction = new MyCustomFunction();
//Register the custom function
wb.RegisterCustomFunction("MyCustomFunction", myCustomFunction);

Code Block

title	VB
language	vb

'Create an ExcelApplication object
Dim xla As New ExcelApplication
 
'Open a workbook containing formulas
Dim wb As Workbook = xla.Open("formulasWorkbook.xlsx")
 
'Create an instance of the custom function implementation
Dim myCustomFunction As IFunction = new MyCustomFunction()

'Register the custom function
wb.RegisterCustomFunction("MyCustomFunction", myCustomFunction)

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