Dynamic Default Values

Sample-Code / Sample-Project

In most cases, it is enough to define static default values, which are known during compile-time.

[OptionDescriptor("count", Required = false, Default = 1)]

However, there are use-cases when you would consider dynamic default values or when a default value depends on another option value.

Imagine your application takes two arguments:

StartDate [mandatory] and EndDate[optional]

If EndDate is not provided in the command-line, it should be Startdate + 7 days. In that case, you cannot define a static default value for Enddate because it depends on another value.

To accomplish this, override the BeforeExecute() method in your Command.

class DateRangeCommand : CommandBase<FromToCommandParameters>
{
    protected override void BeforeExecute(
        TCommandParameters ps,
        HashSet<string> unresolvedPropertyNames,
        ErrorDetailList errors)
    {
        if (unresolvedPropertyNames.Contains(nameof(ps.EndDate)))
        {
            ps.EndDate = ps.StartDate.AddDays(7);
        }
    }
}