Question

I have a very similar function is only one previous report and the other future, how can I optimize and write beautiful?

public bool AnyPreviousReportByGroup(int groupID)
        {
            if(this.GroupID == groupID)
            {
                return true;
            }
            else
            {
                return PreviousReport.AnyPreviousReportByGroup(groupID);
            }
        }

        public bool AnyNextReportByGroup(int groupID)
        {

            if (this.GroupID == groupID)
            {
                return true;
            }
            else
            {
                return NextReport.AnyNextReportByGroup(groupID);
            }
        }

Answer 1

The following code is a conciser way of achieving the same thing:

public bool AnyPreviousReportByGroup(int groupID)
{
    return this.GroupID == groupID ||
           this.PreviousReport != null &&
           this.PreviousReport.AnyPreviousReportByGroup(groupID);
}

If you really want to use lambda expressions, here’s a possible way:

public bool AnyReportByGroup(int groupID, Func<Report, Report> getOtherReport)
{
    if (this.GroupID == groupID)
        return true;

    Report other = getOtherReport(this);
    return other != null &&
           other.AnyReportByGroup(groupID, getOtherReport);
}

You could then call this helper method using lambda expressions:

bool anyPrevious = this.AnyReportByGroup(groupID, report => report.PreviousReport);
bool anyNext = this.AnyReportByGroup(groupID, report => report.NextReport);