Access C# class variables with array like notation?

Question

I have a program in which a user types in the name of the variable they want to change. So we have this:

string user_input = "age";

And I have a class with the following:

class Jim{
    public static int age = 10;
    public static bool married = false;
    public static string name = "John";
}

I now want to print the value of the variable that the user entered. So since the user typed in age I want to print Jim.age. How can I convert user_input into something that lets me access the class. I really want to do Jim[input_string] like you can in JS, but I believe this is possible.

I would use a dictionary to store all of the variables associated with Jim but you can't make a Dictionary which maps as <string, bool or int or string>.

This really isn't the way you should be solving this problem. Some kind of binding, maybe. But trying to reflect based on user input is incredibly dangerous. — Magus, Apr 23 '14 at 17:33
You might want to consider expando objects for this http://msdn.microsoft.com/en-us/library/system.dynamic.expandoobject(v=vs.110).aspx — milagvoniduak, Apr 23 '14 at 17:34
@MyP3uK That wouldn't work here as the variables are static. — Servy, Apr 23 '14 at 17:34
I am not sure if OP needs them to be static taking into account the nature of the data and the class. But you are right it won't work with static. — milagvoniduak, Apr 23 '14 at 17:36
well, you could use an indexer, but you need an instance for that, unfortunately there is no static indexers, so you can't do that. — Selman Genç, Apr 23 '14 at 17:41
Are the fields meant to be static? If not you can use `Indexer` — Sriram Sakthivel, Apr 23 '14 at 17:43

score 2 · Accepted Answer · answered Apr 23 '14 at 17:34

I would use a dictionary to store all of the variables associated with Jim but you can't make a Dictionary which maps as <string, bool or int or string>.

Sure you can, a Dictionary<string, object>. string, bool, and int can all be stored in a variable of type object.

BradleyDotNET · Answer 2 · 2014-04-23T17:41:37.153

The normal way to do this would be to use reflection:

FieldInfo requestedField = typeof(Jim).GetField("age");
Console.WriteLine(requestedField.GetValue(instanceOfJim));

Unfortunately, you can't do this because your variables are static. Make them instance members and it would work. As commenters have noted, allowing users to perform reflection is not a very good idea, so you may want to rethink the use case in general.

You could also use a dictionary mapped to object, as Servy suggested.

Interestingly enough, it can work with static, as long as you put the method in the Jim class:

class Jim
{
   ...Member variables...
   public static GetMember(String name)
   {
      FieldInfo requestedField = typeof(Jim).GetField(name);
      return requestedField.GetValue(null);
   }
}

Again, not recommending this, but it will get the functionality you want.

In case you are wondering, the MSDN for FieldInfo.GetValue: MSDN

Access C# class variables with array like notation?

2 Answers2