R – Why is Windows.Forms in System and not Microsoft

namespacesnetwinforms

I always had the idea that the root namespace in .NET, "System", was mainly for stuff that didn't depend too much on a particular platform.

I was wondering if anyone had any ideas or insight as to why the Windows.Forms namespace is in System and not Microsoft since it seems to be fairly entrenched in one platform.

(No flame wars or unnecessary MS bashing if at all possible please! 🙂 )

Best Answer

I read somewhere that the System.* namespaces are for things that are part of the core .Net framework, whilst the Microsoft.* namespaces are for additional "value-added" optional extras, or things that are in development.

EDIT:

Brad Abrams has a discussion about it in his blog post What Does that .NET Namespace Mean: System.* and Microsoft.*

Additionally, a quote from Visual Basic 2005 with .NET 3.0 Programmer's Reference:

The Microsoft root namespace contains Microsoft-specific items. In theory, any vendor can implement .Net languages that translate into Intermediate Language (IL) code. If you were to build such a language, the items in the Microsoft namespace would generally not apply to your language. Items in the System namespace ... would be as useful to users of your language as they are to programmers who use the Microsoft languages, but the items in the Microsoft namespace would probably not be as helpful.

This would imply that if I was to make a new .Net language, I would be able to make use of the System.Windows.Forms namespace to make UIs, but I would probably not have much use for classes in Microsoft.* namespaces.

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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C# – the difference between String and string in C#

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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