C# and the .NET environment have automatic memory management through garbage collection. Coming from C++ I think it’s great to not having to worry about memory deallocation. Unfortunately memory from the managed heap (which is where C# objects are placed) is just one kind of resource in a system. There are several other types of resources:
These resources still need to be freed in C#. If the .NET class handling the resource is implemented correctly it will release the unmanaged resource when the object is garbage collected. This is fine as long as it doesn’t matter when the resource is freed. In a program with small memory footprint the garbage collector might never run during the execution of the program, because the low memory usage never triggers a run. In the meantime your program can hold on to an expensive database connection instead of releasing it back to the connection pool for reuse. Eventually the database connection pool is empty and your program (or web site) will start failing.