Using Reflection To Find ArrayList Object Properties

Question

What I have is an ArrayList of objects and I am trying to use reflection to get the name of each property of each object in the ArrayList. For example:

private class TestClass
{
    private int m_IntProp;

    private string m_StrProp;
    public string StrProp
    {
        get
        {
            return m_StrProp;
        }

        set
        {
            m_StrProp = value;
        }
    }

    public int IntProp
    {
        get
        {
            return m_IntProp;
        }

        set
        {
            m_IntProp = value;
        }
    }
}

ArrayList al = new ArrayList();
TestClass tc1 = new TestClass();
TestClass tc2 = new TestClass();
tc1.IntProp = 5;
tc1.StrProp = "Test 1";
tc2.IntProp = 10;
tc2.StrPRop = "Test 2";
al.Add(tc1);
al.Add(tc2);

foreach (object obj in al)
{
    // Here is where I need help
    // I need to be able to read the properties
    // StrProp and IntProp. Keep in mind that
    // this ArrayList may not always contain
    // TestClass objects. It can be any object,
    // which is why I think I need to use reflection.
}

Any reason you're using an ArrayList and not a List<TestClass>? — dtb
– dtb, Commented Jun 22, 2011 at 20:23
@dtb - Yes, because my list may not necessarily be a TestClass. It can hold any object. — Icemanind
– Icemanind, Commented Jun 22, 2011 at 20:24
Maybe you could also consider using an interface. But this of course would depend on the situation that you are actually using this for. — Jan-Peter Vos
– Jan-Peter Vos, Commented Jun 22, 2011 at 20:38
@spender - Isn't List<object> basically the same as an ArrayList? Other then maybe for clarity's sake? — Icemanind
– Icemanind, Commented Jun 22, 2011 at 20:39

Marc Gravell · Accepted Answer · 2011-06-22 20:23:46Z

7

foreach (object obj in al)
{
    foreach(PropertyInfo prop in obj.GetType().GetProperties(
         BindingFlags.Public | BindingFlags.Instance))
    {
        object value = prop.GetValue(obj, null);
        string name = prop.Name;
        // ^^^^ use those
    }
}

answered Jun 22, 2011 at 20:23

Marc Gravell

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3 Comments

Icemanind Over a year ago

This might look to be the best answer. I will try it now. Thanks

Icemanind Over a year ago

This works perfect. Only other thing though, Marc, is there a way to know if the property is a string, int, float, decimal, or other (none of the above)?

Marc Gravell Over a year ago

@icemanind well, you could check prop.PropertyType, or more conveniently a switch(Type.GetTypeCode(prop.PropertyType)) which is an enum with most of the common basic types.

Adam Driscoll · Accepted Answer · 2011-06-22 20:24:26Z

1

You could use the as operator so that you don't have to use Reflection.

foreach(object obj in al)
{
     var testClass = obj as TestClass;
     if (testClass != null)
     {
        //Do stuff
     }
}

answered Jun 22, 2011 at 20:24

Adam Driscoll

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5 Comments

Marc Gravell Over a year ago

"Keep in mind that this ArrayList may not always contain TestClass objects. It can be any object," (from the question)

Icemanind Over a year ago

You got "as TestClass", but the List may not have TestClass objects. It may hold a different type of object all together

Adam Driscoll Over a year ago

Casting an object other than a TestClass object would then return null would it not?

Jan-Peter Vos Over a year ago

This might actually be either a great solution or not, depending on the exact intent of the questioner.

Marc Gravell Over a year ago

@Adam - but how would getting a null help achieve the aim of "to get the name of each property of each object in the ArrayList."

FishBasketGordo · Accepted Answer · 2011-06-22 20:23:47Z

0

It's as simple as this:

PropertyInfo[] props = obj.GetType().GetProperties();

The GetType method will return the actual type, not object. Each of the PropertyInfo objects will have a Name property.

answered Jun 22, 2011 at 20:23

FishBasketGordo

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