WPF Binding – Changing property on one object in collection and all the objects are changing

When I change value of textbox or checkbox it changes in every line. Whats wrong?
Here is an examplу: All checkboxes aren’t checked. I click on one of them and all the other are now checked.

Here is the code:

Adding position method:

>Solution :

The problem is because of the below line

spotPosition = AutoTradingPositions.Where(position => 
                          position.PositionNumber == latestPositionNumber).First();

Where you are getting the same instance (first item in the collection) and adding the same as other items to the collection.