CODEWITHSUNDEEP
c#arraysmethodsxnacontains
Matthew K. Crandall
Matthew K. Crandall

Reputation: 86

How do you ask an array if it contains a Specific class?

I am trying to create a "Mario" video game, and in order to obtain intersecting objects, our teacher provided us with an example demonstration, which allows the object to detect if it is touching EXACTLY one other object, and the first object that the method finds, is returned. I am trying, instead to return an array of every object that the current object is currently touching. I was capable of returning an array of every object currently touching it, but now I need an easy/efficient way to check if the array contains an object of a required type, such as 

if (array.Contains(Mario))
    {
    //Do Work here
    }

The array that is being checked if it Contains(Mario), is the returned array of the intersecting Sprites, but when I ask if it actually contains objects of type Mario, it says "Error 14 'WindowsGame10.Mario' is a 'type' but is used like a 'variable' ". I Know I could do this with a for loop, and ask each individual index within the array if (array[i].GetType() == typeof(Mario)), but for the amount of times I would need to perform this check within the code, and retype the same code over and over again, I feel that I need to learn a more efficient way to perform this. I am in my first year of Computer Programming, and I am working with C# XNA, and I need to have some solution that I can understand. If there is a better way to do this, please let me know.

Upvotes: 2

Views: 2482

Answers (5)

Acidic
Acidic

Reputation: 6282

Most straight forward way (without using LINQ) would be to use the is keyword:

foreach (Object obj in array)
{
    if (obj is Mario)
    {
        ...
    }
}

Update: If you need an exact Type match, and want to avoid code duplication, I think a rather simplistic extension method similar to this would be best -

public static bool ContainsType<T>(this T[] arr, Type type)
{
    for (int i = 0; i < arr.Length; i++)
        if (arr[i].GetType().Equals(type))
            return true;
    return false;
}

And the use -

if (array.ContainsType(typeof(Mario)))

Upvotes: 1

Eric J.
Eric J.

Reputation: 150108

The Linq answers are great. Just to provide an alternative approach, you could define an extension method like this:

static public bool ContainsType(this Array array, Type type)
{
    int len = array.Length; // Note that putting this in the loop is slightly slower
                            // because the compiler can't assume that a property value
                            // remains constant.
    for (int i = 0; i < len; i++)
    {
        if (array.GetValue(i).GetType() == type) return true;
    }

    return false;
}

that would be used like this:

    Array a = new object[] { "The meaning of life.", 42 };
    bool hasString = a.ContainsType(typeof(string)); // true
    bool hasInteger = a.ContainsType(typeof(int));  // true
    bool hasChar = a.ContainsType(typeof(char));  // false

Upvotes: 2

labroo
labroo

Reputation: 2961

if you just need to know if there is any Mario then 

if(array.Any(a=>a is Mario))
{
}

this will break out of the iteration as soon it finds the first match.

Upvotes: 2

DaveShaw
DaveShaw

Reputation: 52788

Using Linq you can do:

var marios = array.OfType<Mario>();
if (marios.Any())
{
     //Stuff
}

Upvotes: 4

Reed Copsey
Reed Copsey

Reputation: 564363

You can use LINQ's OfType() and Any() methods:

if (array.OfType<Mario>().Any())
{

Upvotes: 6

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