COmparing List. collection with PropertyInfo.GetType()

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I am looping through property collection using below loop:

C#

foreach (System.Reflection.PropertyInfo eachProperty in this.UIPageAttributes.GetType().GetProperties())
{

}

Now for eachProperty i want to ,compare it against the List<> collection. For checking against any other data type and even for any entity i m using:

C#

if (eachProperty.GetType().Equals(typeof(string))

  if(eachProperty.GetType().Equals(typeof(EntityClass)))
;;;;

But for checking List<> collection type, I didnt find anything where I can directly check for this type,

Any help would be great...

Posted 15-Nov-11 19:40pm

coolsanjay

Updated 15-Nov-11 19:47pm

Pandya Anil

v3

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4 solutions

Solution 4

C#

foreach (System.Reflection.PropertyInfo eachProperty in this.UIPageAttributes.GetType().GetProperties())
{
if (eachProperty.PropertyType == this.EmployeeObject.DepartmentList.GetType())

Solved my problem.

Thanks for suggestions.

Posted 15-Nov-11 23:13pm

coolsanjay

Updated 18-Nov-11 7:22am

v2

Solution 1

you have to implement iComparable Interface in your EntityClass class.

and you have to implement the equals method inside your class, you have to write your own logic to check the equality of two objects.

follow the link to learn more..

http://support.microsoft.com/kb/320727[^]

mark as answer if solves your problem, it motivates :)

Posted 15-Nov-11 19:51pm

Pandya Anil

Comments

Sergey Alexandrovich Kryukov 16-Nov-11 2:50am

Pandya, you did not earn motivation here. Your "solution" won't solve anything. Implementing IComparable is completely redundant and hence wrong. OP needs comparison of classed, not class instances. Same thing about "equals".

Operator "==" does correct comparison for types. OP's problem is completely different, and I've completely solved it. Sorry, this is false solution. It deserves a vote no more than 1, totally negative result.

--SA

Solution 3

If you know the type of elements of the list, you can use typeof(List< TypeHere >). If you just want to check if it is a list, use this: eachProperty.GetType().Name.Equals("List`1")

Posted 15-Nov-11 19:53pm

dan!sh

Comments

Sergey Alexandrovich Kryukov 16-Nov-11 2:53am

Sorry, the solution is all wrong. Comparing anything by name is a bad style and is not really reliable. Also, immediate string constants... very bad. If you mistype, a compiler will never see the problem. Types are reliably compared with "==". Also, this is irrelevant to OP's problem. I solved it completely, please see. I'm really sorry, but this is a false solution, deserves 1. I would better removed it.
--SA

dan!sh 16-Nov-11 3:24am

I agree this is not really a way to do this.
I did not spent time to really analyze what exactly OP is trying to do. I still do not see any need to use reflection here. I understand he wants to format properties as string but why? He might really do well without reflection.

dan!sh 16-Nov-11 3:24am

I will not remove it since people reading will also get to know the wrong way of doing this.

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-11-15T19:53:00

Solution 2

First of all eachProperty has the type System.Reflection.PropertyInfo, not the type it describes. So, eachProperty.GetType() will always return typeof(System.Reflection.PropertyInfo). The type described by this meta-data is eachProperty.PropertyType. Use it to solve your problem.

Some minor problem is using object.Equals for type comparison. It's not good and is even of low performance because its implementation may need to check up type dynamically (you may not care about it, but nevertheless). Instead, use comparison via "==" operator which only works with the type of System.Type and is also more readable.

The ultimate goal of all this activity is not clear (you did not explain it, which is a common mistake) and looks somewhat suspicious to me. Every time the reflected types are explicitly compared suggests it could be OOP violation, a substitution of real OOP design. I cannot say for sure based on your information, so perhaps just think about it.

—SA

Posted 15-Nov-11 19:53pm

Sergey Alexandrovich Kryukov

Updated 18-Nov-11 5:02am

v2

Comments

coolsanjay 16-Nov-11 2:48am

What I wanted to do I will describe now. Lets say we have Employee class with some properties like FirstBName, LastName. Also having one property as Departments which is nothing but List<department>, departments which employee belongs to. Now, I want to return string formatted property name and its corresponding value so instead of hardcoding like string str = "FirstName:" + employee.FirstName i thot to use Reflection and use:
foreach (System.Reflection.PropertyInfo eachProperty in this.EmployeeObject.GetType().GetProperties())
{

}

So properties I am able to fetch using
if (eachProperty.PropertyType == typeof(string) && eachProperty.GetValue(this.EmployeeObject, null) != null &&
!string.IsNullOrEmpty(eachProperty.GetValue(this.EmployeeObject, null).ToString()))

But how to check for List<department>?

coolsanjay 16-Nov-11 2:55am

SAKryukov, Please help me how to solve List<. comparison problem with propertyType.
if (eachProperty.PropertyType == typeof(List<>))?

Sergey Alexandrovich Kryukov 16-Nov-11 3:03am

Yes, what's wrong with this?
--SA

Sergey Alexandrovich Kryukov 16-Nov-11 3:03am

The original idea is in fact good, I appreciate it, the idea of implementation is not.
You need to Reflect the Employee class only once, keep the set of properties to show and get the value and name of each property -- the name only once, but the value each time it is needed. Keep each property in some "reflection cache" type so you won't re-reflect it each time, only use to GetValue.

List is no different, this is the property, so you will get its name in the same way. GetValue will return the instance of the list. The problem is: is the list heterogeneous or not? What do you need to do with the list? If this is only returning the string to present somewhere, do the following: for the type of the element, override object.ToString accordingly. If this is something else, explain what, I would be able to help.

--SA

coolsanjay 16-Nov-11 3:46am

Right now I have written
if(eachProperty.Name.Equals("products")) // products is List<Product>
{
IEnumerable<Product> productList = eachProperty.GetValue(this.UIPageAttributes, null) as IEnumerable<Product>;

int idx = 1;

if (productList != null)
{
foreach (Product eachProduct in productList)
{

string.Format("{0}:{1}|", product.Name,
product.GetValue(eachProduct, null).ToString())
}
}

RaisKazi 18-Nov-11 7:24am

Nice and comprehensive answer. 5ed.

Sergey Alexandrovich Kryukov 18-Nov-11 11:03am

Thank you, Rais.
--SA