When debugging, is there a way to tell if an object is a different instance?

Question

When debugging, I was expecting two different classes to be using the same instance of an object. All of the properties were the same for these two objects, but they were two different instances. Is there a way to tell that in the VS debugger?

In order to tell for sure, I was able to add a field to the class:

private string someId = Guid.NewGuid().ToString();

Then, when debugging, I could at least look at that field for each of the two instances. Is there a better way that wouldn't involve having to create this dummy ID field?

@PeterRitchie So how do you do this in the debugger? The objects, that need to be checked, are in two different classes. — Bob Horn, Mar 22 '13 at 20:09
Shift+F9, type in "Object.ReferenceEquals(obj1, obj2)" and press Reevaluate or Add Watch. Or just type "Object.ReferenceEquals(obj1, obj2)" in the Name column in the Watch window. — Peter Ritchie, Mar 22 '13 at 20:14
possible duplicate of [Uniquely Identifying Reference Types in the Debugger](http://stackoverflow.com/questions/4251450/uniquely-identifying-reference-types-in-the-debugger) — Ian Goldby, Jul 30 '15 at 14:33

score 55 · Accepted Answer · edited Mar 22 '13 at 20:27

55

When debugging, in the Locals window, right-click on the instance and select "Make Object ID".

This will add number that is unique for this instance which is displayed whenever you see this instance in the debugger (in tool-tips as well as in the watch window).

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edited Mar 22 '13 at 20:27

Bob Horn

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answered Mar 22 '13 at 20:10

Wolfgang

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Thanks, but I don't see "Make object ID" when I right-click on the variable when debugging. – Bob Horn Mar 22 '13 at 20:16
Got it! You have to do it in your Locals window: http://blogs.msdn.com/b/zainnab/archive/2010/03/04/make-objectid-vstipdebug0015.aspx. Excellent tip! Thanks! – Bob Horn Mar 22 '13 at 20:18
When you use this option, what happens when the object is disposed? I am debugging some thing related to EF DbContext and it seems that these objects stay in the Locals window, even though (I hope) they were already disposed... – Bartosz Jul 12 '17 at 19:17

A G · Answer 2 · 2013-03-22T20:22:37.133

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Object.Equals Method (Object, Object)

Edit: To check reference equality use ReferenceEquals

Edit 2: While Debugging, Go to debug menu, windows --> immediate window (intellisense should work here) and ?Object.ReferenceEquals(obj1, obj2)

edited Mar 22 '13 at 20:22

answered Mar 22 '13 at 20:01

A G

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That doesn't do it, since it virtual. It can be overridden by a derived class. – John Saunders Mar 22 '13 at 20:02
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Use ReferenceEquals, not Equals. – Eric Lippert Mar 22 '13 at 20:04
Can anyone confirm if (object)p1 == (object)p2; will achieve the same thing, but a little faster? I don't remember 100%. – A G Mar 22 '13 at 20:10
+1 for the tip, but Wolfgang's answer was exactly what I was looking for. Thanks! – Bob Horn Mar 22 '13 at 20:23

score 2 · Answer 3 · answered Aug 10 '15 at 23:57

In addition to the answers above, you can also compare pointers. If you have two objects obj1 and obj2, you can check (e.g. in Watch Window) their addresses with: &obj1 and &obj2.

Note that objects may be moved around by the .NET runtime, so two address checks of the same object separated with some code execution in between may result in different addresses.

When debugging, is there a way to tell if an object is a different instance?

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