C# Attributes

Front 1

What general kinds of attributes are there?

Back 1

Predefined or custom.

Front 2

What are the reserved attributes?

Back 2

There are only two reserved attributes, Conditional and Obsolete.

Front 3

Give an example of attribute usage, i.e., show a code snippet.

Back 3

[Obsolete] public myClass { ... };

//This class should not be used.

or

[Conditional("Debug")] void DebugTrace() { ... }

Compile this method only if the Debug flag is defined.

Front 4

What types of declarations can an attribute target?

Back 4

Most declarations. A complete list can be found at: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/csref/html/vclrfattributetargets.asp

Front 5

Can all attributes be used on all targets?

Back 5

No. Most attributes must be attached to a specific language element. However, there are some global attributes.

Front 6

To what elements do global attributes apply?

Back 6

Assemblies or modules.

Hint 6

This is pretty high level stuff.

Front 7

Name two global assembly attributes.

Back 7

The following are found in the System.Reflection namespace.

AssemblyConfigurationAttribute
AssemblyCultureAttribute
AssemblyDescriptionAttribute
AssemblyKeyFileAttribute
AssemblyKeyNameAttribute
AssemblyDelaySignAttribute
AssemblyTitleAttribute
AssemblyVersionAttribute

Front 8

What System.Reflection attributes are used with the strong name tool?

Back 8

AssemblyKeyFileAttribute
AssemblyKeyNameAttribute
AssemblyDelaySignAttribute

Use the file name from the SN.exe (strong name utility) as arguments to these attributes.

Front 9

How can you create your own custom attributes.

Back 9

Create a class that inherits form the System.Attribute class.

Hint 9

It's a classy act.

Front 10

Give a quick code example that builds a custom attribute

Back 10

using System;
//restrict attribute usage to classes only
[AttributeUsage(AttributeTargets.Class)]
public class myClass(string astring)
{
//constructor
public Collector(string astring
{
this.astring = astring;
date = 1993;
}
//private versions of parameters
public short date;
string astring;
}

Front 11

How is name space collision avoided when building attributes?

Back 11

All attributes implicitly end with "Attribute". Thus "Collector" from the example will be treated as "CollectorAttribute" by the system.

Hint 11

The Attributes are implicitly obvious.

Front 12

What System.Reflection method is used to retrieve attribute information from Attributes?

Back 12

Either
public virtual object[] GetCustomAttributes(bool);
or
public static Attribute GetCustomAttribute(Assembly, Type);

Front 13

What are the two types of parameters that are supported by Attribute Classes?

Back 13

Positional Parameters:
a. Must be specified when the attribute is used.
b. Must be set by constructor.

Named Parameters:
a. optional
b. when specified name of parameter must be specified. i.e., foo = foovalue
c. named parameters are similar to properties. But defined at the class level.

Hint 13

Ya gotta do it or maybe you don't.

Front 14

What types may an attribute argument be?

Back 14

Simple numeric types including char.
string
System.Type
enums
object
one-dimensional arrays of any of the above types.

Hint 14

KISS

Front 15

Where can you find the acceptable values for the AttributeTargets attribute?

Back 15

AttributeTargets enumeration

Hint 15

Look in online help.

Front 16

If you wanted to create a attribute that could be used more than once how would you do it?

Back 16

[AttributeUsage(AttributeTargets.All,AllowMultiple = true)]
Note: AllowMultiple must be named.