Such a thing as a calculation engine for C#?

Is there any calculation engine for C# that can automatically recalculate dependent fields when a value changes?

Let me freestyle for a second, I'm imagining something like this..

 Field<double> quantity = Field.Create<double>("Quantity");
 Field<double> unitCost = Field.Create<double>("Unit Cost");
 Field<double> total = Field.Create<double>("Total");

 total.Calculation((q,uc) => q * uc, quantity, value);
      // would have signature something like this:
      // void Calculation<TR,T1,T1>(Func<TR,T1,T2>, Field<T1>, Field<T2>)

This would set up fields that auto-propagate dependent values.

 quantity.Value = 5.0;
 unitCost.Value = 1.5;
 Assert.That(total.Value, Is.EqualTo(7.5));

Obviously this is a simple example, the end uses would be much more akin to the calculations of a complex spreadsheet.

Thinking further it would be amazing if the field/cells would support change notification.

c# propagation

Edit Report

Have you seen http://ncalc.codeplex.com ?

It's extensible, fast (e.g. has its own cache) enables you to provide custom functions and varaibles at run time by handling EvaluateFunction/EvaluateParameter events. Example expressions it can parse:

Expression e = new Expression("Round(Pow(Pi, 2) + Pow([Pi2], 2) + X, 2)");

  e.Parameters["Pi2"] = new Expression("Pi * Pi");
  e.Parameters["X"] = 10;

  e.EvaluateParameter += delegate(string name, ParameterArgs args)
    {
      if (name == "Pi")
      args.Result = 3.14;
    };

  Debug.Assert(117.07 == e.Evaluate());

It also handles unicode & many data type natively. It comes with an antler file if you want to change the grammer. There is also a fork which supports MEF to load new functions.

It also supports logical operators, date/time's strings and if statements.

a solution

You could possibly do automatic recalculation by implementing INotifyPropertyChanged then doing something like

set a field's expression this.Field.Expression = new Expression("Field1+Field2");

On notifypropertyupdated in the class

for each field (with reflection) that is a Function
if it's expression refers to the changed field then recalculate the variable.
on recalculation you'd need to handle the EvaluateParameter event to use reflection to find the right field and extract its value (you could cache to avoid reflection if needed)

answered 2011-02-01T16:26:52.077

Such a thing as a calculation engine for C#?

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