Revisiting C# Script Performance

This is another often overlooked feature in our reporting tool List & Label – you can add scripts to your projects and use your favorite language to do so. Since a couple of versions already, List & Label supports C# Scripts. However, the performance was less than perfect, making it a good choice for complex calculations but not so much for using it on a line-to-line base. In List & Label 26, we were able to push the performance quite remarkably – now using scripts is perfectly feasible.

One reason why many people overlook the scripting feature is that it is opt-in. For security reasons, we decided to default the availability to false. Switching it on is just a matter of setting the option LL_OPTION_SCRIPTENGINE_ENABLED (index 276) to 1. Let’s do a quick walkthrough, using the “order list with scripting” sample report of the demo application. It displays the order number, order and delivery date and a script-powered calculation of the number of working days between those two dates.

The last column in the report just reads:

ScriptVal ("CSharpScript", LoadFile$ (ProjectPath$() + "WorkingDays.cs"))

That means, load the WorkingDays.cs script from within the project path and return its value. So let’s dig into the script. The crucial part is the Main() method:

static void Main()
{
var workDayCalc = new WorkingDaysCalculator();
WScript.Result = workDayCalc.Calculate(Report.Field("Orders.OrderDate"), Report.Field("Orders.ShippedDate"));
}

The WorkingDaysCalculator is just a simple class to calculate the working days in a quite simple manner. The more interesting part is the usage of the Report object that’s added dynamically. It has a couple of methods:

Using these methods, you can easily interact with the report and your data. And by setting WScript.Result, you can return a value for the ScriptVal function as shown above.

Additionally, there is also the possibility of debugging your scripts. All you have to do is add the line

<!--#pragma debugmode-->

at the very beginning of the script. This will automatically include the following code at the start of the Main() method which will start a suitable debugger (if there is one installed on your system), attach it to the LL process, and break before any of the actual code gets executed.

System.Diagnostics.Debugger.Launch();
if (System.Diagnostics.Debugger.IsAttached)
{
System.Diagnostics.Debugger.Break();
}

Looking forward to seeing more usage of this hidden gem in the future :-).

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