.net – What are the pros/cons of 64 bit .NET

32-bit64-bitnet

As mentioned in this question/comments there are certain disadvantages when moving from 32 bit .NET to 64 bit .NET.

Probably the biggest advantage is the much bigger process address space in the 64 bit world, but what other pros and cons are worth noting?

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I've seen it to be noticeably faster (~ 4x in my experience) for some computationally-heavy (number-crunching) applications. The best thing is it comes for free in pure managed cases. You don't even have to recompile anything to get the benefits. Also, I've heard that the x64 JIT has more aggressive optimizations.

The biggest disadvantage is probably not being able to load 32-bit COM components in process.

This is the style that Microsoft tends to use in their examples.

It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

C# – the difference between const and readonly in C#

Apart from the apparent difference of

having to declare the value at the time of a definition for a const VS readonly values can be computed dynamically but need to be assigned before the constructor exits.. after that it is frozen.
const's are implicitly static. You use a ClassName.ConstantName notation to access them.

There is a subtle difference. Consider a class defined in AssemblyA.

public class Const_V_Readonly
{
  public const int I_CONST_VALUE = 2;
  public readonly int I_RO_VALUE;
  public Const_V_Readonly()
  {
     I_RO_VALUE = 3;
  }
}

AssemblyB references AssemblyA and uses these values in code. When this is compiled:

in the case of the const value, it is like a find-replace. The value 2 is 'baked into' the AssemblyB's IL. This means that if tomorrow I update I_CONST_VALUE to 20, AssemblyB would still have 2 till I recompile it.
in the case of the readonly value, it is like a ref to a memory location. The value is not baked into AssemblyB's IL. This means that if the memory location is updated, AssemblyB gets the new value without recompilation. So if I_RO_VALUE is updated to 30, you only need to build AssemblyA and all clients do not need to be recompiled.

So if you are confident that the value of the constant won't change, use a const.

public const int CM_IN_A_METER = 100;

But if you have a constant that may change (e.g. w.r.t. precision).. or when in doubt, use a readonly.

public readonly float PI = 3.14;

Update: Aku needs to get a mention because he pointed this out first. Also I need to plug where I learned this: Effective C# - Bill Wagner

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This is the style that Microsoft tends to use in their examples.

C# – the difference between const and readonly in C#

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