Generating properties of a class dynamically - C# Discussion Boards

Generating properties of a class dynamically

26-Jun-13 16:24

There's a whole article here on CodeProject[^] on how to do just that.

0bx26-Jun-13 12:19

0bx

26-Jun-13 12:19

Over the project I created several classes and enum's; I hope it's bit self-explanatory:

public enum weaponType{unarmed, dagger, sword, club, axe};
public enum monsterType{ rat, bat, humanoid, feline, beast };

class weapon : item
{
   private weaponType type;
   public weaponType Type
   {
      get { return type; }
      set { type = value; }
   }

   private int requiredSkill;
   public int RequiredSkill
   {
      get { return requiredSkill; }
      set { requiredSkill = value; }
   }
   ...
}

class actor
{
    private name;
    public Name{ get{return name; } set { name = value;} }
    ...

    private int daggerSkill;
    public int DaggerSkill { get{return name; } set { name = value;} }
    private int swordSkill;
    ...
}

class monster : actor
{
   private monsterType;
   ...
}

class player : actor
{
   private ratKills...
}

"Actors" need to have all the "weaponType-Skills" additionally, the player needs to have all the "monsterType-Kills" as separate properties.

However, I would like to freely add and remove items from those enum's without much overhead; because the overhead would increase exponentially if the project becomes more complex.

So what I rather like to do is the compiler to iterate through the enum and generate all the extra properties like "Skill" and "Kills" dynamically and to be able to use them as if they're fully written out.

So far I haven't been able to figure out how, or if, this can be done programmatically; without resorting to make some code generator.

As usual, any help is much appreciated.

Ron Beyer26-Jun-13 14:37

26-Jun-13 14:37

So why not use a List<string> for the skills. For example:

public class actor
{
    private List<string> skills = new List<string>();

    public bool HasSkill(string skill)
    {
        return skills.Contains(skill);
    }

    public void AddSkill(string skill)
    {
        skills.Add(skill);
    }

    public void RemoveSkill(string skill)
    {
        skills.Remove(skill);
    }
}

Etc... That way you don't have to modify the system to add skills, it just works.

Is there a way to generate classes and properties dynamically? Yes, but its really not easy, requires use of low level MSIL and some pretty good knowledge of CodeDOM, really more of a headache than its worth.

0bx26-Jun-13 16:11

0bx

26-Jun-13 16:11

Thanks for your reply.

I can't use that because Skills will be integers.

But you gave me the idea to use an array instead. It would look something like this: int[skillType.Length - 1].
It's indeed good enough and still pretty easy to make.

I've done some assembler in the past, but I don't know MSIL. I was hoping there's some function in the .NET library that could do it; but I couldn't find it.

Ron Beyer26-Jun-13 16:18

26-Jun-13 16:18

Its because it's not there, it would be nice to be able to add properties to a type at runtime but you can't. You can generate them dynamically, but you have to generate the entire class (although you could use derived classes for base functionality).

There are other things you can do dynamically, such as anonymous types, but I don't think they would fit the bill since you have to know all the properties at instantiation. Instead of using an array of integers, you can also use an array of your skill enum. That way you don't have to type cast later and you can extend just by adding elements to your enum. Another way would be to add the Flags attribute to your enum, then you can combine flags, like:

enum Skills { skill1, skill2, skill3, skill4 }

//Then in your class:
private Skills mySkills = Skills.skill1 | Skills.skill2;

//Which now holds both skills

You can then use the Skills.HasFlag to determine if any of the flags (skills) are set.

Freak3027-Jun-13 2:47

Freak30

27-Jun-13 2:47

I think a Dictionary<string,int> would be more appropriate. This way you can save the skills of your player object to disc and reload them later, even after you have added more possible skills. You could of course also use an enum as key instead of the string as suggested.

C# select excel file from directory path

0bx28-Jun-13 3:01

0bx

28-Jun-13 3:01

Been working on this for two days now, so it's a bit too troublesome to go back and review the core after I got it all working. I'm indeed using enum's as a key to translate raw csv into useful game data.

The downside is that making some changes like removing or switching around items may indeed break existing game-files, but it's not a big issue since everything else scales just fine.
Not expecting this will become a problem though. I'll put a version tag on everthing just in case.

classy_dog26-Jun-13 10:56

classy_dog

26-Jun-13 10:56

In a C# 2010 desktop application, I want to change the application so that it will only allow users to select a
report that meets the following criteria:
1. part of the file name is "ErrorReport" and
2. The last node of the file name is .xlsx or .xls.

So far I have the following code:

string[] excelFiles = Directory.GetFiles(strDirectoryLoc, "*ErrorReport*")
                                         .Select(path => Path.GetFileName(path))
                                         .Where(x => (x.EndsWith(".xlsx") || x.EndsWith(".xls"))
                                                   && (!x.StartsWith("~")))
                                         .ToArray();

This code works when I am selecting only excel (*.xls or *.xlsx) files.

The problem occurs if the user selects a .pdf file iniitally and there is actually a file in the directory path
that meets the criteria I listed above. The code will ignore the .pdf file the user selects and will actually use the
excel file that is in the directory path.

Thus how can I change the code listed above to say the .pdf file is invalid?

Re: C# select excel file from directory path

Ron Beyer26-Jun-13 15:26

26-Jun-13 15:26

I think you are looking for something like:

string[] excelFiles = Directory.GetFiles(strDirectoryLoc, "*ErrorReport*")
                                         .Select(path => Path.GetFileName(path))
                                         .Where(x => (x.EndsWith(".xlsx") || x.EndsWith(".xls"))
                                                   && (!x.StartsWith("~") && x.Contains("ErrorReport")))
                                         .ToArray();

You can also use Path.GetFilenameWithoutExtension and check that the string has ErrorReport in it.

2 way events

bfis10813726-Jun-13 8:56

bfis108137

26-Jun-13 8:56

Is there such a thing as 2 way events? OR maybe I am doing this wrong. My form is making a call to a dll to submit a form and logon to a web site if required. The dll all of a sudden needs more information that wasn't thought it would need prior so it wants to ask the user for more information and then continue when it has it. I have searched around for 2 way events with no luck. I started to make an event that calls back to the form and then the form calls back with the new information to a continuation event but then I started to realize that there are issues with this such as another function called the logon function and the form doesn't know about that. Obviously I could track that as well. In any event I would like to know if I am doing it the wrong way.

Ron Beyer26-Jun-13 9:12

26-Jun-13 9:12

Events are always "2 way", meaning they are raised and returned.

Maybe you are getting terms mixed up, you don't call functions by using events (or if you are, its not the right design). You should have a way of validating your user input before pushing up the call stack to the DLL to make sure you get everything you need.

Can you give a specific scenario? Here's how it reads to me:

Your application asks me for some information, like username/password. I give it. You pass it to the DLL to submit some information to a web-site and this DLL needs additional information to complete the call, like saying "not registered, please create an account". You need the additional account information so you ask the user for it and call again.

In that case, I would expect that the DLL function returns something that says it needs more data. You simply ask the user for it, and re-submit to the same function. If you are subscribing to an event in the DLL that says "succeeded" "failed", or "additional info" then it really is a violation of programming principles since how are you supposed to match up a function call with a request if you have multiple happening at the same time?

I guess I would need more information to be able to suggest a good course of action here, is the DLL yours or third party?

bfis10813726-Jun-13 10:34

bfis108137

26-Jun-13 10:34

Well in this case it's a captcha. So I don't know if it will even be required for 1 and 2 I need the user to solve it.

Dave Kreskowiak26-Jun-13 12:10

Dave Kreskowiak

26-Jun-13 12:10

Events are alwyas "2 way", though they are never described as such.

There is always an event provider and one or more subscribers to that event. The event usually passes the source of the event (usually as Object) and some kind of EventArgs object. What you may not realize is that you can modify the Eventargs object passed to your event handler. When the event handler code goes out of scope, the event provider gets control back and can look at the data that is in the EventArgs object it sent to the handler. For an example of this, see Form_Closing and it's FormClosingEventArgs class. In there, you'll find a Cancel property that the handler code can set to cancel the form being closed.

Another example is KeyPressEventArgs and its Handled property.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak