WPF dynamically create formula in TextBox

Question

I'm working on a project where the user needs to have the ability to create a formula in a WPF app. The formula has to be made from some properties. Let's say we have properties:

public decimal? Prop1 { get; set; }
public decimal? Prop2 { get; set; }
public decimal? Prop3 { get; set; }

Now, let's say we have a TextBox where the user has to be able to input only those properties and in between of the there needs to be some of the operators: +, -, /, *.

I got the part where the user can only input those values properties and operators… But my problem is how can I save that formula to the SQL database (lets say Prop1 * Prop2), how can I get the formula from database and make it read the values from the and basically "do the math…"

decimal? x = MyFormula;

I know the question is difficult, and so is my description of my it… Please feel free to ask for more detail if needed, and I'll try to explain it.

You can run javascript formula in C#, just need to replace PropX placeholders with values from properies. Look into this https://stackoverflow.com/questions/4744105/parse-and-execute-js-by-c-sharp for more details. — just-my-name, Dec 07 '18 at 14:27
@just-my-name Yes, basically that's what I want, but I'm searching for that "replace"... That's with what I'm struggling — sharp, Dec 07 '18 at 14:49
I've used ironpython for what sounds like a similar requirement. If it fits what you want to do it is easy to implement. https://weblogs.asp.net/dfindley/Using-IronPython-for-Dynamic-Expressions_2E00_ — Andy, Dec 07 '18 at 15:42

Paul Michaels · Answer 1 · 2018-12-07T13:17:56.680

There's two distinct questions there, and they're both a bit open ended.

My suggestion for your first question would be to serialise the Model / ViewModel to a string. You might find that you want to store them slightly differently. For example:

public class Property
{
    public string PropReference{get;set;}
}

public class Operator
{
    public string Operator{get;set;}
}

public class Calculation
{
    public Property Prop {get;set;}
    public Operator Op {get;set;}
    public Property Prop2 {get;set;}
}

That way you can chain them together, and even nest them. In answer to your second question, you might want to investigate a library such as Jace, as this isn't an easy problem, but has already been solved.

EDIT - Alternative solution based on comments:

public class Operator : IAction
{
    public string Operator {get;set;}
}

public class Calculation : IAction
{
    IList<KeyValuePair<IAction, Property>> Operations {get;set;}
}

Yes, I was thinking about similar, but the difference is that there can be an > 1 operator or even none. And the calculation too, more than one Property and none or more types of Calculation — sharp, Dec 07 '18 at 13:10
You could potentially make the Proprty/Operator a kvp list, which would easily allow chaining. If you also need nesting you could simply reference a Calculation from within Calculation — Paul Michaels, Dec 07 '18 at 13:15

WPF dynamically create formula in TextBox

1 Answers1