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    <p>Apologies for the short answer, but no, the C# language specification disallows it.</p> <p>See this <a href="https://stackoverflow.com/questions/340528/c-automatic-properties-why-do-i-have-to-write-get-set/340682#340682">answer</a> to another question to see what happens when you try. It also says why you shouldn't make the property just be a public field to get around the restriction.</p> <p>Hope this helps</p> <p><strong>EDIT: You ask Why?</strong></p> <p>You pass a variable to an <code>out</code> or <code>ref</code> parameter you're actually passing the address (or location in memory) of the variable. Inside the function the compiler knows where the variable really is, and gets and writes values to that address.</p> <p>A property looks like a value, buts it's actually a pair of functions, each with a different signature. So to pass a property, you'd actually need to pass two function pointers, one for the get, and one for the set. </p> <p>Thats a completely different thing to pass to a function than the address of a variable</p> <p>i.e. one variable address v's two function pointers.</p> <p><strong>Update</strong><br> <em>Why doesn't C# just look after this for us?</em></p> <p>I'm no <a href="https://stackoverflow.com/users/88656/eric-lippert">Eric Lippert</a>, but I'll have a go at why</p> <p>What should the signature of the function you're calling be?<br> Lets say you want to call <code>void MyFn(ref int i)</code> should that remain that way, or should it change to say we also allow properties? If it changes to some syntax like <code>void MyFn(prop_ref int i)</code> then this is fairly useless, you can't pass properties to library functions or 3rd party code that wasn't written with the special prop_ref modifier. Anyway I think you're suggesting it shouldn't be different. </p> <p>Now lets say <code>MyFn</code> passes <code>i</code> to a COM function, or WinAPI call, passing the address of <code>i</code> (i.e. outside .net, by ref). If it's a property, how do you get the address of <code>i</code>? There may be no actual int under the property to get the address of. Do you do what VB.Net does? </p> <p>The Vb.Net compiler spots when a property is passed as a ByRef argument to a method. At that point it declares a variable, copies the property to the variable, passes the variable byref and then after the method is called, copies the variable back into the property. i.e.</p> <pre><code>MyFunc(myObject.IntProperty) </code></pre> <p>becomes</p> <pre><code>Dim temp_i As Integer = myObject.IntProperty MyFunc(temp_i) myObject.IntProperty = temp_i </code></pre> <p>Any property side effects don't happen until <code>MyFunc</code> returns, which can cause all sorts of problems and lead to <em>very</em> subtle bugs.</p> <p>In my humble opinion the Vb.Net solution to this problem is also broken, so I'm not going to accept that as an answer.</p> <p>How do you think the C# compiler should handle this?</p>
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    1. POIs it possible to pass properties as "out" or "ref" parameters?
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    1. POIs it possible to pass properties as "out" or "ref" parameters?
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    1. COThis is broken. C# is not a low level language, so a `ref` parameter should not be an address, but actually a pair of closures, a getter and a setter. If you pass a local variable as a `ref` parameter, the language should automatically create a getter/setter pair. And all this should be hidden from the unsuspecting programmer.
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    2. CO@Eduardo León: I've updated my answer.
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    3. CO@EduardoLeón: There are many things which can be done with addresses which cannot be done with closures. The proper way to allow properties to be passed as references would be to define a kind of property which, rather than containing a getter and setter, would expose an address in controlled fashion (e.g. a property of type T could have a method which, given a delegate that accepted a ref parameter of type T, would pass the address of that property's backing field (or other storage location of type T) to that delegate.
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