CODEWITHSUNDEEP
c#asp.net
Frank Grech
Frank Grech

Reputation: 35

Is it possible to make use of a list from an object by its object type?

I am trying to delete items from different lists og objects. I have the below classes, in my case I will be given the the object name of the list and then I will be required to delete items from that list. Is it possible to access a specific list only by its object type?

As an example I will be given "TestSubcolleciton" and then i will have to access Subcollecitons list in order to delete some records. 

       private class TestClassWithSubcollection : BaseObject
        {
            public List<TestSubcolleciton> Subcollecitons { get; set; }

            public List<TestSubcollecitonSecond> SubcollecitonSeconds { get; set; }
        }

        protected class TestSubcolleciton
        {
            protected int Id { get; set; }
        }

        protected class TestSubcollecitonSecond
        {
            protected int Id { get; set; }
        }

Upvotes: 0

Views: 67

Answers (1)

CSharpie
CSharpie

Reputation: 9467

This can be done using reflection, though this is probably a bad idea.

public static IList GetListByItemType(object instance, Type listItemType)
{
    if(instance == null) throw new ArgumentNullException("instance");
    if(listItemType == null) throw new ArgumentNullException("listItemType");

    Type genericListType = typeof(List<>).MakeGenericType(listItemType);
    PropertyInfo property = instance.GetType().GetProperties().FirstOrDefault(p => p.PropertyType == genericListType);
    if(property != null)
      return (IList)property.GetValue(instance);
    return null;
}

This either returns null or the first reference of a List found.

You can then use it like this:

TestClassWithSubcollection instance = ...

IList list = GetListByItemType(instance, typeof(TestSubcollecitonSecond));

if(list != null)
{
    // ...
}

If you need to get it by "Type name" of the list Item then do it like this:

public static IList GetListByItemType(object instance, string listItemTypeName)
{
    if(instance == null) throw new ArgumentNullException("instance");
    if(listItemTypeName== null) throw new ArgumentNullException("listItemTypeName");


    PropertyInfo property = instance.GetType().GetProperties().FirstOrDefault(p => p.PropertyType.IsGenericType && p.PropertyType.GetGenericArguments()[0].Name== listItemTypeName);

    if(property != null)
        return (IList)property.GetValue(instance);
    return null;
}

This is then used like this:

IList list = GetListByItemType(instance, "TestSubcollecitonSecond");

if(list != null)
{
    // ...
}

Upvotes: 1

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