Size of a class in c#

Hi,

OK, to each data member that is an object type we get 32 bits allocated (on a 32 bit system) or 64 bits allocated (on a 64 bit system). For each value type, we get the size of the value type. Therefore:

class something
{
string str1;
string str2;
string str3;
Int64 int1;
}

will give us 3 x 4 bytes for the strings (internally stored as a pointer to the string, i.e a memory address) and 64 bits (8 bytes) for the Int64. So we can roughly estimate this class will take up 20 bytes on the heap.

However, take a look at the class below:

class parent
{
someclass child1;
someclass child2;
}

In this case the someclass members are objects, so although each on takes up ~ 20 bytes the parent class needs only 8 bytes - enough to store two pointers.
creating an instance of parent takes up at least 8 bytes - even if the someclass members are not initialised.

in terms of time taken, the clock cycles used to allocate the memory are very few - allocating and freeing memory is generally a rapid operation.

we ourselves cannot enhance the speed of the compiler (it is very fast anyway) but you can certainly enhance the speed of the program by following some guidelines:

* create child classes only when needed. in the case of 'parent' above, don't created child1 and child2 in the constructor - create them only when required.
* make (very) small classes structures. if we have the class 'vector'
class vertex
{
int x;
int y;
int z;
}
it is so small (~12 bytes) that the saving in storing as a pointer (12-4 = 8 bytes) is very small - if we're doing lots of work with vertex objects, manipulating, copying, passing them around, we will in general be faster defining them as 'structures' so that they are copied by value (i found this out the hard way with a c# openGL port).

also look into 'boxing' and 'unboxing' - there is an overhead in converting a value to an object and vice versa, i.e.

function(object o)
{
...
}

int i = 0;
function(i);

in this case we have to 'box' i (which is a value) into an object to be passed to function.

For sure, although you'll need the right version of visual studio (Ultimate or Premium).

The task you are looking at is known as 'profiling', which involves running the application whilst visual studio (or another profiling tool) gathers low level data about how the CPU is being hit.

It's a complicated area, so the best I can do is suggest looking at:

http://msdn.microsoft.com/en-us/library/ms182372.aspx

and taking it from there :) Good luck!