C# – Can’t find `DataProtectionScope` and `ProtectedData` classes in System.Security.Cryptography

ccryptographyvisual studio 2010

I've referred the file System.Security.dll as described in this article but according to my IDE, the line using System.Security.Cryptography; can be safely removed as it's not being used.

The same IDE tells me that I've got an error with DataProtectionScope and ProtectedData. Those are supposed to be in that namespace. However, when I dot my way through the packages, I can't see them in there.

Is the article wrong? How can I access the two classes?

Best Answer

As @Coral Doe mentioned in a comment under @Dave Lucre:

"Had a similar problem and this worked. using System.Security.Cryptography; didn't [show] me [ProtectedData] and ProtectedMemory until I had referenced the System.Security.dll for the specific framework."

This fixed the issue for me. Specifically, I performed these steps:

Open the project in Visual Studio.
Right-click the project's name in Solution Explorer then choose Properties.
Click the References tab on the left.
Click the Add button.
Click the .NET tab.
Select System.Security and click OK to add the reference.

Hope this helps.

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

Best Answer

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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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