asked on

Advanced Reflection with Generics - nested IList

I am trying to work with reflection and am trying to create a helper method for my unit tests to print out all the properties of an object. Some objects have nested collections - of type IList - and I want to be able to iterate through those as well.

The code snippet below is what I'm using. The first line in the 2nd foreach loop is where I'm trying to determine if the property I'm inspecting is an IList - and if it is - I want to make the recursive call.
------------
foreach (PropertyInfo p in props)
{
//check to see if its of type IList and make a recursive call
if (p.PropertyType.IsGenericType)
{
// recursive call to PrintListProperties<p.type?>((IList)p," ");
}

------------
How could I go about doing this? I've tried a couple things but can't seem to figure it out.

public static void PrintListProperties<T>(IList<T> list, string indent)
        {
            PropertyInfo[] props;
            string s = "";
            string padding = "";
 
            foreach (var t in list)
            {
                props = t.GetType().GetProperties();
                
                Console.WriteLine(indent + "\n-------New Property---------");
                foreach (PropertyInfo p in props)
                {
                    //check to see if its of type IList and make a recursive call
                    if (p.PropertyType.IsGenericType)
                    {
                    }
 
                    s = string.Format("{0}={1} ", p.Name, p.GetValue(t, null));
                    padding = "";
                    if (s.Length < 20)
                    {
                        for (int i = 0; i < 20 - s.Length; i++)
                            padding += " ";
                    }
                    else
                    {
                        padding = "\n";
                    }
 
                    Console.Write(indent + s + padding);
                }
            }
        }

Open in new window

Jaime Olivares

Have a look to this code snippet:

object obj = ......; // some object inherited from IList

System.Reflection.PropertyInfo countprop = obj.GetType().GetProperty("Count", typeof(int));
if (countprop == null)
return;

int count = (int)countprop.GetValue(obj, null);
if (count<1)
return;

System.Reflection.PropertyInfo indexer = obj.GetType().GetProperty("Item", new Type[] { typeof(int) });
if (indexer == null)
return;

for (int i = 0; i<count; i++)
{
object value = indexer.GetValue(obj, new object[] { i });
// do something with value
}

bswiftly

ASKER

ok, so that isn't working for me.

I created a method with the code above, and the first line always returns null and skips out of the function.

This is my object roughly -

public class User()
{
public FirstName {get;set;}
public IList<Task> Tasks {get;set;}
}

So when i get to the Tasks (or for other objects with a generic list of different type) I'd like to print out all the properties of each Task object.

Jaime Olivares

which element is obj?:
User
Firstname
Tasks

bswiftly

ASKER

Tasks.

It is 'p' in the 2nd foreach loop (the PropertyInfo).

Jaime Olivares

can you debug where the function returns?
does Tasks have some contents?

bswiftly

ASKER

Yes, I've been stepping through it. There is no property "Count" on that object.

Busac

To rely on the Count property is not a good idea because:

1. Types that don't implement IList<> may have a property called Count.
2. Types that do implement IList<> may not have a property called Count. (They could implement IList<>.Count explicitly.)

To find out if the p.PropertyType is IList<> or implements IList<>, you can do the following:

if ((p.PropertyType.IsGenericType && p.PropertyType.GetGenericTypeDefinition() == typeof(IList<>)) || p.PropertyType.GetInterface("IList`1") != null) {
// recursive calls
}

The first part checks if PropertyType is IList<> and the second part checks if PropertyType implements IList<>. (The second part returns false if PropertyType is IList<>, that's why you need the first check.)

The next step would be getting the value of the property and casting it to IList<T>. For this you need to figure out what type T needs to be, I would advise on looking into the GetGenericArguments() method or maybe the GetInterfaceMap() method, I'm not sure how to do this yet but I'll be back in a while if you won't be able to continue.

Busac

Also one thing to clarify - suppose you have an instance of the following type:

public class MyClass()
{
public object Data {get;set;}
}

and you assign an instance of IList<> to its Data property:

MyClass c = new MyClass();
c.Data = new List<string>();

Do you want your PrintListProperties method to make a recursive call on the Data property or not? In other words, do you only want to check the declared return type of the property or also check the runtime type of the property value?

bswiftly

ASKER

Thanks - I haven't figured this out yet but looks like a better solution.

I don't really care about that example you showed - I'm really only looking for the declared type - as these are all for business objects and there won't be any 'object' objects hanging around.

Thanks for the help so far, hopefully you have some time to continue - I'll let you know if I come up with something.

ASKER CERTIFIED SOLUTION

Busac

membership

This solution is only available to members.

To access this solution, you must be a member of Experts Exchange.

Start Free Trial

bswiftly

ASKER

Hey thanks..

That works - the only thing I had to change was my declaring class of course, and then I had overridden the PrintListProperties method so it was returning 2 objects not just one and I had to get rid of the overriden method.

Thanks man.. I appreciate the help!

Busac

No problem, I'm happy to hear it worked. If you have any related problems don't hesitate to post here ;-).