• Source 
    1. using System;
    2. using System.Reflection;
    3.  
    4. [AttributeUsage(AttributeTargets.Class | AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
    5. class HelpAttribute : Attribute
    6. {
    7. 	public string field = "field";
    8.  
    9. 	public string Help
    10. 	{
    11. 		get;
    12. 		set;
    13. 	}
    14.  
    15. 	public HelpAttribute()
    16. 	{
    17. 		Help = "no help";
    18. 	}
    19.  
    20. 	public HelpAttribute(string help)
    21. 	{	
    22. 		this.Help = help;
    23. 	}
    24. }
    25.  
    26. [Help]
    27. class ClassWithCustomAttribute
    28. {
    29.  
    30. 	public ClassWithCustomAttribute()
    31. 	{
    32. 		ReadAttributes();
    33. 		// Method invoked only when debugging
    34. 		MethodDebug();
    35. 	}
    36.  
    37. 	[Obsolete("This method should not be used anymore!", true)]
    38. 	public void Method0()
    39.     { 
    40. 		// do smth
    41. 	}
    42.  
    43. 	[System.Diagnostics.Conditional("Debug")]
    44. 	public void MethodDebug()
    45. 	{
    46. 		Console.WriteLine("Method for debug!");
    47. 	}
    48.  
    49. 	protected void ReadAttributes()
    50. 	{
    51. 	    // if  AllowMultiple = false but inherited is true the base class Help is overridden by the Derive class Help attribute.
    52. 		Console.WriteLine("Assigned attributes of "+this+": ");
    53. 		foreach(HelpAttribute attr in this.GetType().GetCustomAttributes(true))
    54. 		{
    55. 			Console.WriteLine("\tHelp: \t" + attr.Help);
    56. 			Console.WriteLine("\tField: \t"+attr.field);			
    57. 		}
    58. 	}
    59. }
    60.  
    61. [Help(field = "Some help field")]
    62. class DerivedClassWithCustomAttribute : ClassWithCustomAttribute
    63. {
    64. 	public DerivedClassWithCustomAttribute()
    65. 	{
    66. 		ReadAttributes();
    67. 	}
    68. }
    69.  
    70. public class Test
    71. {
    72. 	public static void Main()
    73. 	{
    74.  
    75. 		ClassWithCustomAttribute cca = new ClassWithCustomAttribute();
    76. 		// OUTPUT:
    77. 		// Assigned attributes: 
    78. 		// 		Help: 		no help
    79. 		// 		Field: 		field
    80.  
    81. 		DerivedClassWithCustomAttribute dca = new DerivedClassWithCustomAttribute();
    82. 		// OUTPUT:
    83. 		// Assigned attributes of DerivedClassWithCustomAttribute: 
    84. 		// 		Help: 	no help
    85. 		//		Field: 	Some help field
    86.  
    87. 		// In case the Inherited option of AttributeUsage applied to HelpAttribute 
    88. 		// we would get following output when invoke ctor of DerivedClassWithCustomAttribute:
    89. 		// OUTPUT:
    90. 		// Assigned attributes of DerivedClassWithCustomAttribute: 
    91. 		// 		Help: 	no help
    92. 		// 		Field: 	Some help field
    93. 		// 		Help: 	no help
    94. 		// 		Field: 	field
    95.  
    96. 	}
    97. }