Cancellation Token Support

NCalc allows passing a CancellationToken when creating or evaluating an expression. The token is forwarded to the parser and to all custom evaluation handlers invoked during Evaluate or EvaluateAsync.

NCalc does not cancel execution by itself except at parsing. Subscribers are responsible for honoring the token inside their handlers.

Example

var cts = new CancellationTokenSource();

var expression = new AsyncExpression("getUserName(1) == 'admin'");
expression.Functions["getUserName"] = async args =>
{
    var id = (int)(await args[0].EvaluateAsync(args.CancellationToken)!)!;

    args.CancellationToken.ThrowIfCancellationRequested();

    using var db = new AppDbContext();

    return await db.Users
        .Where(u => u.Id == id)
        .Select(u => u.Name)
        .FirstAsync(args.CancellationToken);
};

var result = await expression.EvaluateAsync(args.CancellationToken);

Learn more about cancellation tokens

Microsoft docs: https://learn.microsoft.com/dotnet/api/system.threading.cancellationtoken