string is an alias in C# for System.String.
So technically, there is no difference. It's like int vs. System.Int32.
As far as guidelines, it's generally recommended to use string any time you're referring to an object.
e.g.
string place = "world";
Likewise, I think it's generally recommended to use String if you need to refer specifically to the class.
e.g.
string greet = String.Format("Hello {0}!", place);
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.
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
Best Solution
I have written most of the code for horn and the objective is to be a package manager with an analogy with rubygems.
We want to up OSS adoption by making it ridiculously obvious to get and use OSS packages.
For example if I want Nhibernate we can simply command:
horn -install:nhibernate
etc.
We also want to smooth the upgrade path.
A lot of .NET OSS uses other OSS and they generally all have differing version of oss.
For example MVCContrib might use one version of Castle, rhino might use another and Nhibernate might use another.
If we do the following:
horn -install:nhibernate horn -install:rhino horn -install:mvccontrib
Then we should all have the same versions of all .dlls.
So to sum up, we want to get packages and make sure that all packages we get from horn have the same version of dependencies e.g. Castle.
The way horn works is by downloading all source code to the client and building it.
Our next steps are to turn horn into a server tool.