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    <blockquote> <p>The address of pr declared in each loop will be stored by the list.</p> </blockquote> <p>No, it won't. The <em>value</em> of the <code>pr</code> variable at the point at which <code>Add</code> is called will be stored in the list. That value is a reference - a reference to the new object you've created.</p> <p>It's important to understand that the value of a variable in C# is <em>never</em> an object. It's always either a value type value, or a reference. Once you get your head round that - and start being very clear about the differences between variables, their values, references, and objects - a lot of things (parameter passing, assignment, garbage collection etc) become much clearer.</p> <p>For example, consider:</p> <pre><code>Button x = new Button(); Button y = x; </code></pre> <p>There's only one <em>object</em> here - the <code>Button</code> created on the first line. There are two <em>variables</em> (<code>x</code> and <code>y</code>) and after the second line they both have the same value (a reference to that object) because of the assignment. They're still independent variables though (assigning a new value to <code>x</code> won't change <code>y</code>). Think about how that is applied to your example - you're calling <code>pl.Add(pr)</code> which just passes the <em>value</em> of <code>pr</code> to the <code>Add</code> method. After that, the <code>pr</code> variable is <em>completely irrelevant</em> as far as the list is concerned. So you could have:</p> <pre><code>pl.Add(pr); pr = null; </code></pre> <p>and the second line wouldn't affect the list at all.</p>
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    1. COThank you very much! I need to digest it a bit. I guess simply thought List the same as an array but with no pre-defined size.
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    2. COThank you so much for your elaboration. It has become much clearer now.
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    3. CO@JuntingZhu: Arrays behave in the same way in terms of storing references. So if you had an array and used `array[0] = pr;` that would still just store the current *value* of `pr`.
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