Under the Hood of .NET Memory Management - Simple Talk

Chapter 4: Common Memory Problems
Types
The type system in .NET consists of value and reference types: a value type is a primitive
or struct, and a reference type is a pointer. In practical terms, while a value type will
simply represent the current value for whatever variable you are dealing with, reference
types are a bit more complicated. There are two components to the data in a reference
type, specifically, the reference and the actual data. The reference is stored in the stack,
and it contains the memory location (in the heap) where the data is actually stored.
A type itself describes the possible data that it can hold, along with the operations it can
perform on that data. Every variable has a type that fully describes it, and it may also have
types that provide a partial description, such as an interface.
DateTime valueType = DateTime.Now;
IComparable partialDescription = valueType;
List referenceType = new List();
IEnumerable partialDescription2 = referenceType;
Listing 4.1: Switching from the type to an interface.
In this example, valueType is a DateTime and so can do anything that a DateTime
can do, but partialDescription is an IComparable and can only do what an
IComparable can do, even though both variables have the same data and refer to the
same location in memory.
Let's take a look at these two main .NET types, and see how their nature and operations
can give rise to bugs and memory leaks.
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