How much memory does a C#/.NET object use?

Question

I'm developing an application which currently have hundreds of objects created.

Is it possible to determine (or approximate) the memory allocated by an object (class instance)?

Answer 1

You could use a memory profiler like

.NET Memory Profiler (http://memprofiler.com/)

or

CLR Profiler (free) (http://clrprofiler.codeplex.com/)

Answer 2

Here's a related post where we discussed determining the size of reference types.

Answer 3

If you can - Serialize it!

Dim myObjectSize As Long

Dim ms As New IO.MemoryStream
Dim bf As New Runtime.Serialization.Formatters.Binary.BinaryFormatter()
bf.Serialize(ms, myObject)
myObjectSize = ms.Position

Answer 4

To get a general sense for the memory allocation in your application, use the following sos command in WinDbg

!dumpheap -stat

Note that !dumpheap only gives you the bytes of the object type itself, and doesn't include the bytes of any other object types that it might reference.

If you want to see the total held bytes (sum all the bytes of all objects referenced by your object) of a specific object type, use a memory profiler like dot Trace - http://www.jetbrains.com/profiler/

Answer 5

There is the academic question of What is the size of an object at runtime? And that is interesting, but it can only be properly answered by a profiler that is attached to the running process. I spent quite a while looking at this recently and determined that there is no generic method that is accurate and fast enough that you would ever want to use it in a production system. Simple cases like arrays of numerical types have easy answers, but beyond this the best answer would be Don't bother trying to work it out. Why do you want to know this? Is there other information available that could serve the same purpose?

In my case I ended up wanting to answer this question because I had various data that were useful, but could be discarded to free up RAM for more critical services. The poster boys here are an Undo Stack and a Cache.

Eventually I concluded that the right way to manage the size of the undo stack and the cache was to query for the amount of available memory (it's a 64-bit process so it is safe to assume it is all available) and then allow more items to be added if there is a sufficiently large buffer of RAM and require items to be removed if RAM is running low.

Answer 6

The ANTS memory profiler will tell you exactly how much is allocated for each object/method/etc.