# AsyncCustomFunction ## Content

Class AsyncCustomFunction

java.lang.Object
com.grapecity.documents.excel.CustomFunction
com.grapecity.documents.excel.AsyncCustomFunction
public abstract class AsyncCustomFunction extends CustomFunction
Represents the base type for an asynchronous custom function.

Extend this class and override evaluateAsync(Object[],ICalcContext) to provide the calculation logic. After the function is registered, formulas can call the function and return the result.

Parameters cannot accept cell or range references. Use calculated values as arguments instead, and do not access workbook model objects inside the asynchronous logic because it may run on another thread.


 class AsyncAddFunction extends AsyncCustomFunction {
     public AsyncAddFunction() {
         super("ASYNCADD", "Adds two numbers asynchronously.", FunctionValueType.Number,
             new Parameter[] {
                 new Parameter(FunctionValueType.Number),
                 new Parameter(FunctionValueType.Number)
             });
     }

     protected CompletableFuture<Object> evaluateAsync(Object[] arguments, ICalcContext context) {
         double left = ((Number) arguments[0]).doubleValue();
         double right = ((Number) arguments[1]).doubleValue();
         return CompletableFuture.completedFuture(left + right);
     }
 }

 AsyncCustomFunction function = new AsyncAddFunction();
 Workbook.AddCustomFunction(function);
 worksheet.getRange("A1").setFormula("=ASYNCADD(10,20)");
 Object sum = worksheet.getRange("A1").getValue();