Reflection...

Today I got the question from a collegue if it was possible to instantiate a class, based on a result from a computation, without making use of an if-then-else, case or any other (logical) construction.


We found the answer in using reflection and attributes.
first of all, we created a class "ClassType":

<br />[AttributeUsage(AttributeTargets.Class)]<br /> public class ClassType : System.Attribute<br /> {<br /> string[] _types;<br /><br /> public ClassType (params string[] types)<br /> {<br /> this._types = types;<br /> }<br /><br /> public string[] types<br /> {<br /> get { return _types; }<br /> }<br /> }<br />

After that, we created some classes, with each its own attribute:
<br />[ClassType ("Type", "A")]<br /> public class test :System.Attribute<br /> { <br /> }<br /><br /> [ClassType ("Type", "B")]<br /> public class Dog : test<br /> {<br /> <br /> public Dog()<br /> { <br /> <br /> }<br /> }<br /><br /> [ClassType ("Type", "C")]<br /> public class Cat : test<br /> {<br /> public Cat()<br /> {<br /><br /> }<br /> }<br />

after that, the attributes of a class in a certain assembly can be read (a little bit of pseudo code ;)

<br />public class ReadAttribute<br /> {<br /> public ReadAtt()<br /> {<br /> // pseudo code<br /> foreach(Class class in Assembly)<br /> { <br /> System.Reflection.MemberInfo memberInfo = typeof(class);<br /> object[] attributes = memberInfo.GetCustomAttributes(typeof(ClassType), false);<br /> <br /> foreach (Object attribute in attributes)<br /> {<br /> ClassType aliasAttribute = attribute as ClassType ; <br /> }<br /> } <br /> }<br /> }<br />