Compiles into a library defining the RamdomSupplier attribute
and the RandomMethod attribute
/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
Example17_5a compiles into a library defining the RamdomSupplier attribute
and the RandomMethod attribute
*/
using System;
// declare an attribute named RandomSupplier
[AttributeUsage(AttributeTargets.Class)]
public class RandomSupplier : Attribute
{
public RandomSupplier()
{
// doesn't have to do anything
// we just use this attribute to mark selected classes
}
}
// declare an attribute named RandomMethod
[AttributeUsage(AttributeTargets.Method )]
public class RandomMethod : Attribute
{
public RandomMethod()
{
// doesn't have to do anything
// we just use this attribute to mark selected methods
}
}
//===================================================
/*
Example17_5b implements one class to supply random numbers
*/
// flag the class as a random supplier
[RandomSupplier]
public class OriginalRandom
{
[RandomMethod]
public int GetRandom()
{
return 5;
}
}
//===================================================
/*
Example17_5c implements one class to supply random numbers
*/
using System;
// flag the class as a random supplier
[RandomSupplier]
public class NewRandom
{
[RandomMethod]
public int ImprovedRandom()
{
Random r = new Random();
return r.Next(1, 100);
}
}
// this class has nothing to do with random numbers
public class AnotherClass
{
public int NotRandom()
{
return 1;
}
}
//===================================================
/*
Example17_5d illustrates runtime type discovery
*/
using System;
using System.Reflection;
class Example17_5d
{
public static void Main(string[] args)
{
RandomSupplier rs;
RandomMethod rm;
// iterate over all command-line arguments
foreach(string s in args)
{
Assembly a = Assembly.LoadFrom(s);
// Look through all the types in the assembly
foreach(Type t in a.GetTypes())
{
rs = (RandomSupplier) Attribute.GetCustomAttribute(
t, typeof(RandomSupplier));
if(rs != null)
{
Console.WriteLine("Found RandomSupplier class {0} in {1}",
t, s);
foreach(MethodInfo m in t.GetMethods())
{
rm = (RandomMethod) Attribute.GetCustomAttribute(
m, typeof(RandomMethod));
if(rm != null)
{
Console.WriteLine("Found RandomMethod method {0}"
, m.Name );
}
}
}
}
}
}
}
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