Why are objects apparently cloned by collection initializer for List<>?>

Question

In the following code, why is pdList[0] null while _propertyDetails is a properly instantiated object? I was under the impression that I'm adding a reference to pdList that points to the same object as _propertyDetails , so after instantiating this object, both references should be non-null?

PropertyDetailsModel _propertyDetails = null;
var pdList = new List<PropertyDetailsModel> { _propertyDetails };
_propertyDetails = PropertyDetailsModel.Read(PropertyId);

Forgive me if I'm missing something basic; I've been battling to narrow my problem down to this issue for several hours, and my brain is tired.

Answer 1

When you initialise the list, it is not _propertyDetails that goes into the list, but the thing that _propertyDetails is currently a reference to (which is null in this example, but the point remains). Making _propertyDetails refer to a different thing later doesn't change what's in the list.

Answer 2

It's (apparently) a reference type, so when you create pdList , the reference gets copied, but it is null at that point. Assigning to _propertyDetails later does not change the null reference that's already in pdList .

Answer 3

_propertyDetails is not an properly instantiated object. It's not an object at all. It is a reference which points to nothing which is called null in C#. To get an object, you would have to write something like

PropertyDetailsModel _propertyDetails = new PropertyDetailsModel();

Answer 4

As others have said, you're getting confused between a variable and its value. You don't need to use lists to demonstrate this - it's equivalent to this code:

string foo = null;
string bar = foo;
foo = "Hello";

Console.WriteLine(bar); // Empty, as the value of bar is null

Changing the value of a variable is not the same thing as changing the data within an object that the variable refers to.