I am looking for an open source library to parse and execute formula/functions in C#.
I would like to create a bunch of objects that derive from an interface (i.e. IFormulaEntity) which would have properties/methods/values and the allow a user to specify formulas for those objects.
For example, I might have
public class Employee : IForumulaEntity
{
public double Salary { get; set; }
public void SendMessage(string message)
}
Then allow an application user to write something like;
Employee person = <get from datasource>
if (person.Salary > 1000)
person.Salary += 1000;
person.SendMessage("Hello");
This "looks like C#" but it would be a simplified programming language. I know it's alot to ask. I would expect my users to be reasonably capable (i.e. can write their own Excel formulas).
Look into the Rules Engine functionality that is part of Windows Workflow Foundation.
This is not a place one would think to look. However, as part of the work they did to produce a UI that allows a Workflow developer to use configurable rules and expressions, they've come up with a way to do the same thing in your own application, even if you are not using Workflow at all. Their documentation includes examples of hosting this functionality in a Windows Forms application.
I've used ANTLR, FSLEX/FSYACC and Managed Babel. All do what you are asking, and while all are free, only the first is open source.
Antlr: http://antlr.org/
FSLEX: http://www.strangelights.com/fsharp/wiki/default.aspx/FSharpWiki/fslex.html
Managed Babel: http://msdn.microsoft.com/en-us/library/bb165963.aspx
You could use cs-script. This allows you to execute c# code, that is maybe more then you want, but why not just stick to c# instead of creating your own c#-like syntax. It is possible to integrate cs-script into your application as DLL and you can allow it to execute c# code that is not part of a class so that users can just write the few statements they need.
Spring expressions are very powerful, and less of an all or nothing than e.g. WF
(The engine is ANTLR based, and the expressions bit, while it pulls in a decent sized lib, doesnt yank in all of Spring.NET)
While I'm beating this to death, Dynamic LINQ plays in this space (specifically the C# like syntax). Obviously be careful that it's requirements (emission/compilation of code) are supported in your context.
Related
We have a MS SQL 2005 database. The data is uploaded in this database from Excel sheets. These Excel sheets come from various vendors and most of them never maintain a predefined structure so that we can create a separate insertion/update module.
Until now I have created a module which accepts an Excel sheet in a predefined format and uploads the data from it. For every vendor someone has to format it in the predefined manner manually which takes too long and is a donkey work.
Now we have removed the manual formatting and put all database columns in one column, and drop-downs containing all Excel columns in another column. The user maps the desired columns and updates the database.
But most of the time this simple mapping falls short, since mostly we have to split/combine values based on some logic. To make it more user friendly and since most of my users are themselves C# programmers I have decided to remove the drop-downs and use text boxes where users can enter direct logic. For example:
dbcol1 = excel[col1].ToString().Replace("-"," ")
+(int.Parse( excel[col6].ToString())*.1).ToString();
While searching for this I came across dynamically compiling C# code. Since I have never done so before and also I am not sure that this method will be efficient I need to know that am I moving in the right direction with this. Or is there a more efficient and faster way to do this?
Script it up? C# Script is pretty handy, if you want to compile and run code on the fly;
If you can string format something that is correct C# it'll let you compile and run it.
http://www.csscript.net/
For example:
dynamic script = CSScript.Evaluator
.LoadMethod(#"void SayHello(string greeting)
{
Console.WriteLine(greeting);
}");
script.SayHello("Hello World!");
Probably not great for production, but you can at least prototype your idea
Normally you would use Reflection.Emit to generate a .NET assembly on the fly and execute that. However, it accepts only Intermediate Language instructions, not C#. And creating a whole new assembly each time you want to execute a piece of code is not efficient at all.
Roslyn is Microsoft's attempt at a compiler as a service. This is a new rewritten compiler for C# and VB.Net that can be called by an application to compile code, and it provides information about the code it is compiling.
Anders Hejlsberg (I believe) showed an example using the Roslyn compiler to implement a C# scripting interface: type some C# and it gets executed on the fly. While Roslyn is still in development, you might want to see if it would meed your needs by trying the Roslyn CTP.
C# as a Scripting Language in Your .NET Applications Using Roslyn is a CodeProject article that goes into some detail.
Finally, if you cannot (yet) or don't want to use Roslyn, or if it does not provide the execution speed you were looking for, then I think your best bet (in terms of performance) is to parse and interpret the scripting code yourself. However, this is error-prone hard work.
I have the situation that the same repeating refactoring tasks have to be done for a huge number of methods in my code.
For example imagine a interface with 100 methods, each of them has one or more parameters as well as a return value. For each of these methods I need to jump to the implementation change the return type and add a line of code which converts the old return value to its new type for callers of the interface method.
Is there any way to quickly automate such refactorings?
I even thought to write a custom script to do it, but writing a intelligent script would approximately take longer than doing it maually.
A tool supporting such task can save a lot of time.
It's a good question, but in the time it took since you posted it (not to mention the time you spent searching for an answer before posting), you could have completed the changes manually.
I know, I know, it's utterly unsatisfying, but if you think of it as a form of mediation, and only do this once a year, it's not that bad.
If your problem is one interface with 100 methods, then I agree with another poster: just doing it may seem painful but it is limited in effort and you can be done really soon.
If you have this problem repeatedly, or you have very large code base (many, many interfaces for which you want to perform this task), then what you need is a tool for implementing automated change: a program transformation engine. Such a tool provides the ability to parse source code, build a program representation (an abstract syntax tree), and enables one to apply "scripted" operations on the tree either through procedural interfaces and/or through source-to-source transformation patterns.
OUr DMS Software Reengineering Toolkit is such a program transformation system. It has a C# Front End to enable its application to C# code. Configuring such a tool for a complex task is not a matter of hours, so it is not useful for "small scale" changes. For large scale changes, such tools can make it possible to do things simply not practical by hand.
Resharper and CodeRush both have features which can help with this kind of task.
Resharper's change signature functionality is probably the closest match.
Can't you generate a new interface from the class you have and then remove the ones you don't need! if it's that simple!!
change the return type : by changing... the return type, provided it is not a standard type (...), and the converter can be implemented by a TypeConverter.
When i have such boring task to do, i often switch VS2010 and use a tool that allow regex search and replace. In your example, maybe change 'return xxx;' by 'var yyy=convert(xxx); return yyy;'
(for example editor Notepad++ (free) allready offers quite some possiblities to change everything in a project (use with caution))
I'm creating a piece of software (written in C#, will be a windows application) and I ran into this problem-
I've got a set of variables, and I need to allow the user to define a wide range of mathematical functions on those variables.
But my users don't necessarily have to have any prior knowledge about programming.
The options I've considered are:
Create some sort of GUI for defining the mathematical "functions". But that is very limiting.
Implement a very simple embedded language, that will offer flexibility while remaining relatively easy to understand. I looked at Lua, but the problem with that is that you pretty much need to have prior knowledge in programming. I was thinking about something more readable (somewhat similar to SQL), for example "assign 3 to X;"
Other ideas are welcome.
I'm basically looking for the best way to go here, under the assumption that my users don't have any knowledge in programming.
However, note that this is not the main feature of my software, so I'm assuming that if a user wants/needs to use this feature, he will take the time to look at the manual for a few minutes and learn how to do so, as long as it's not too complicated.
Thanks, Malki :)
What you want is a domain specific language. I see you've tried Lua and didn't find that acceptable--I'll assume that most pre-built scripting languages are out then.
Depending on your expected function complexity, I would recommend that you give a shot at implementing a small recursive-descent parser so that you can exactly specify your language. This way you can realize something like:
assign 3 to X
show sin(X * 5)
If this is a bit beyond what you're willing to do, you can get some parsing assistance from a library such as Irony; this will let you focus on using the abstract syntax tree rather than playing with tokenizing/lexing for some time.
If you want, you can even look at FLEE, which will parse and evaluate some pretty complex expressions right out of the gate.
ANTLR is a greate parser if you want to make your own language
I'm writing a small visualization tool in wpf, the idea is that average users can create interesting visualizations without being programming wizards.
I have a controller class that has methods like StartPath(double x, double y) and LineTo(x,y) CurveTo(...) etc.
The idea is that a user can type these commands into a textbox and have it draw the result on a canvas.
StartPath(0,0);
LineTo(30,50);
LineTo(50,40);
EndPath();
One Idea I had was to use a .cs template that has all the methods implemented, and has an additional Run() command with a replacement token inside. I load the template as a string, insert the user commands into the Run() method, use the new .net 4.0 compilation service to create an assembly on the fly, then load it and invoke its Run() method and access the exposed Path to draw it on a canvas.
Another one would be to actually just parse the textbox, error check it and call the appropriate methods.
Are there any other methods, especially with the new dynamic keyword?
You don't need to use anything new from .NET 4.0. The ability to compile C# code in the framework has been present for ages. In fact, my Snippy tool does pretty much exactly what you say - it's a template that user code goes in. You're welcome to base your tool on mine, should you wish to. You can download the code from the C# in Depth site.
Aside from anything else, that way you won't require your users to have .NET 4.0.
As for dynamic - it doesn't really help in this case, unless you fancy letting your users write code in IronPython/IronRuby. C# still doesn't have a sort of "eval" call letting you just execute an arbitrary string.
I think you are better to try to define a LL1 language and generate a parser and a scanner and build your own interpreter.
Coco/R is a very stable and well known tool for this kind of job.
Check this out is should not be difficult for what you have in mind:
http://www.scifac.ru.ac.za/coco/cshcoco.htm
If you want to use the new dynamic you will still have problem parsing the input command text.
You could use dynamic to build your interpreter on top of the parser.
Hope this helps
I'm just starting out with C# and to me it seems like Microsoft Called their new system .Net because you have to use the Internet to look everything up to find useful functions and which class they stashed it in.
To me it seems nonsensical to require procedure/functions written and designed to stand alone ( non instantiated static objects) to have their class not also function as their namespace.
That is Why can't I use Write or WriteLine instead of Console.WriteLine ?
Then when I start to get used to the idea that the objects I am using ( like string) know how to perform operations I am used to using external functions to achieve ( like to upper, tolower, substring, etc) they change the rules with numbers, numbers don't know how to convert themselves from one numeric type to another for some reason, instead you have to invoke Convert class static functions to change a double to an int and Math class static functions to achieve rounding and truncating.. which quickly turns your simple( in other languages) statement to a gazillion character line in C#.
It also seems obsessed with strong typing which interferes somewhat with the thought process when I code. I understand that type safety reduces errors , but I think it also increases complexity, sometimes unnecessarily. It would be nice if you could choose context driven types when you wish without the explicit Casting or Converting or ToStringing that seems to be basic necessity in C# to get anything done.
So... Is it even possible to write meaningful code in notepad and use cl with out Internet access? What ref book would you use without recourse to autocomplete and Network access?
Any suggestions on smoothing the process towards grokking this language and using it more naturally?
I think you're suffering a bit from the fact that you've used to working in one way during some years, and now must take time to get yourself comfortable using / developing in a new platform.
I do not agree with you , that MS hasn't been consistent on the fact that a string knows how it should convert itself to another type, and other datatypes (like ints) do not.
This is not true, since strings do not know for themselves how they should be converted to another type as well. (You can use the Convert class to Convert types to other types).
It is however true that every type in .NET has a ToString() method, but, you should not rely on that method to convert whatever you have to a string.
I think you have never worked in an OO language before, and therefore, you're having some difficulties with the paradigm shift.
Think of it this way: it's all about responsabilities and behaviour. A class is (if it is well designed) responsible for doing one thing, and does this one thing good.
There is no excuse to use notepad to code a modern language. SharpDevelop or Visual C# Express provide the functionality to work with C# in a productive way.
And no, due to the complexity, not using the internet as a source of information is also not a good option.
You could buy a book that introduces you to the concepts of the language in a structured way, but to get up-to-date information, the internet is neccessary.
Yes, there are drawbacks in C#, like in any other language. I can only give you the advice to get used to the language. Many of the drawbacks become understandable after that, even if some of them don't become less annoying. I recommend that you ask clear, direct questions with example code if you want to know how some language constructs work or how you can solve specific problems more efficiently. That makes it easier to answer those questions.
For notepad, I have no useful advice, however I would advise you to use one of the free IDE's, Microsofts Express Editions, or Sharp Develop.
The IDE will speed the groking of the language, at which point, you can switch back to notepad.
Reading your post I was thinking that you worked mostly with C or dynamic languages previously. Maybe C# is just a wrong choice for you, there are IronPython, F# and a bunch of other languages that have necessary functionality (like functions outside of classes etc.)
I disagree with you about consistency. In fact there are small inconsistency between some components of .NET, but most part of FW is very consistent and predictable.
Strong typing is a huge factor in low defect count. Dynamic typing plays nice in small/intermediate projects (like scripts, etc). In more or less complex program dynamism can introduce a lot of complexity.
Regarding internet/autocomplete - I can hardly imagine any technology with size of .NET that doesn't require a lot of knowledge sources.
Programming in c# using notepad is like buying a ferrari to drive in dirt roads.
At least use Visual Studio Express Edition. For what you wrote I understand that you come from a non OO background, try to learn the OO concept and try to use it. You will eventually understand most design decisions made for .Net.
http://en.wikipedia.org/wiki/Object-oriented_programming
Oh boy where do i start with you(this will be a long post hahaha), well, lets go little by little:
"Microsoft called their system .NET because you have to use Intenet...", the reason why is called .NET is because the SUITE OF MICROSOFT LANGUAGUES(and now some other ones too like Phyton and Ruby, etc) CAN CALL ANY LIBRARY or DLLs, example you can "NET"(Network OR CALL) a DLL that was built in Visual Basic, F#, C++ from WITHIN C# or from any of those languagues you can also call(or ".NET") C# libraries. OK ONE DOWN!!!
NEXT ONE: "it seems nonsensical to require....to have their class not also function as their namespace", this is because a Namespace can have AS MANY CLASSES AS YOU WISH, and your question:
"That is Why can't I use Write or WriteLine instead of Console.WriteLine ?".
The reason is because: "Console"(System.Console hense the "Using" statement at the beginning of your program) Namespace is where "Write" and "WriteLine" LIVES!!(you can also FULLY qualify it (or "call It"). (all this seems to me that you need to study C# Syntax), ok NEXT:
"when I start to get used to the idea that the objects...", ok in simple words:
C# is a "Strongly Type-Safe language" so that SHOULD-MUST tell you what "you are getting in to" otherwise STAY WITH "WEAK or NO TYPE SAFE LANGUAGES" LIKE PHP or C , etc. this does NOT means is bad it just MEANS IS YOUR JOB TO MAKE SURE, as i tell my students: "IF YOU NEED AN INT THEN DEFINE AN INT INSTEAD LETTING THE COMPILER DO IT FOR YOU OTHERWISE YOU WILL HAVE A LOT OF BAD BUGS", or in other words do YOUR homework BEFORE DESIGNING A PIECE OF SOFTWARE.
Note: C# is IMPLICITY TYPE SAFE language SO IF YOU WANT YOU CAN RUN IT AS UNSAFE so from then it wiLL be your job to make sure, so dont complain later(for being lazy) when bugs arrive AT RUNTIME(and a lot of times when the customer is already using your crappy software).
...and last but not least : Whey do you wan to shoot yourself by using notepad? Studio Express is FREE, even the database SQL SERVER is FREE TOO!!, unless you work for a company I WILL ASK FOR PRO, ETC. all the "extra" stuff is for large companies, teams, etc, YOU CAN DO 99% OF THE STUFF WITH THE FREE VERSIONS(and you can still buy-update to full version once you want to scalate to Distributed Software or a Large Project, or if your software becomes a big hit, Example: if you need millions of queryes or hits PER SECOND from your database or 100 people are working on same project(code) but for the majority of times for 2 or 3 "normal" developers working at home or small office the FREE ONES ARE ENOuGH!!)
cherrsss!!! (PS: Software Developer since the 80's)