C# array of different objects

Question

I have 2 classes B and D. I have to create an array with 4 elements 2 of type B and 2 of type D. How do I do it?

B o1 = new B();
D o2 = new D();
B o3 = new B();
D o4 = new D();

The array should be something like this:

array[0] = o1; array[1] = o2; array[2] = o3; array[3] = o4;

I need to study for an exam. And couldn't find the answer on google. :) — Paul Moldovan
– Paul Moldovan, Commented Jun 28, 2013 at 8:45
Answer would be: makes only sense, if B and D inherit from A (class or interface), then create array of A. Although B and D inherit from Object, Object has to few properties to be useful here. — JeffRSon
– JeffRSon, Commented Jun 28, 2013 at 8:51
I am new to c#. I don't like it but I have to learn it. In PHP it's 10000 times easier; I am new to PHP. I don't like it. C# is 10000 times easier ;) — Nolonar
– Nolonar, Commented Jun 28, 2013 at 8:56

Jon Skeet · Accepted Answer · 2013-06-28 08:41:57Z

14

If there is no common base class other than object, you just need:

object[] array = new object[4];
array[0] = o1;
// etc

Or in a single shot:

object[] array = { o1, o2, o3, o4 };

To use the members specific to B or D, you'd need to cast when you retrieved the values from the array, e.g.

B b = (B) array[0];
b.SomeMethodDeclaredOnB();

If B and D have common methods, you could declare those in an interface which both classes implemented, and change the type of the array:

IBD[] array = new IBD[4];
array[0] = o1;
...
array[0].SomeMethodDeclaredInIBD();

Or:

IBD[] array = { o1, o2, o3, o4 };
...
array[0].SomeMethodDeclaredInIBD();

Finally, to address this:

I am new to c#. I don't like it but I have to learn it. In PHP it's 10000 times easier;

I'm sure if I tried to use PHP I'd find the same experience in the exact opposite direction. Don't assume that C# is "worse" or "harder" than PHP - it's just different, and you're bound to find it harder to use a language you're not familiar with than your "comfort zone" language.

edited Jun 28, 2013 at 8:41

answered Jun 28, 2013 at 8:36

Jon Skeet

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11 Comments

Paul Moldovan Over a year ago

In PHP it's like this: $array = array($o1, $o2, $o3, $o4); Much simpler. After that I can do this: $array = "here is a string". And The variable array changed it's type. Simple. Elegant. Easy to find on the web :)

Jon Skeet Over a year ago

@PaulMoldovan: And easy to make mistakes with. Don't underestimate the power of static typing. There's a simpler way to declare and populate the array in one go in C# as well - I'll edit that in.

Paul Moldovan Over a year ago

Maybe you're right. But after i pass this exam I'll go back to my normal life. A PHP developer. :P

Jon Skeet Over a year ago

@PaulMoldovan: I think it's a pity if you don't use the opportunity you're being given to expand your horizons. It's always useful to see a different perspective on development. But if this is really just a means to an end as far as you're concerned, that's your call. I just think you're missing out.

Brian Over a year ago

@PaulMoldovan: I suppose if you heavily abused the dynamic keyword, you could pretend that C# was a dynamically typed language. However, this will have heavy performance penalties and will make debugging your program much more difficult. Also, other C# developers will come after you with torches and pitchforks.

|

Tigran · Accepted Answer · 2013-06-28 08:37:40Z

4

or use array object[] array of objects
or more OOP approch:

public class B : IHolder { }

public class D : IHolder { }

IHolder[] arrays of IHolders

answered Jun 28, 2013 at 8:37

Tigran

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Comments

CodeCaster · Accepted Answer · 2013-06-28 08:39:15Z

1

I am new to c#. I don't like it but I have to learn it. In PHP it's 10000 times easier;

You left out a part of the last sentence: "to make mistakes". Strong-typedness has its strengths.

You can let the classes B and D inherit from a common base class or interface like such:

interface ISomeInterface
{
    string CommonProperty { get; }
}

class B : ISomeInterface
{
    public string CommonProperty { get; }
}

class D : ISomeInterface
{
    public string CommonProperty { get; }
}

ISomeInterface[] array = new ISomeInterface[]
{
    o1,
    o2,
    o3,
    o4
}

answered Jun 28, 2013 at 8:39

CodeCaster

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