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Assembly custom attributes helper

Submitted by Tomasz Paprocki on 16 February, 2011 - 14:14
in

From this article you can learn how to define and use simple helper. Example shows generic methods returning list of any type of Attribute from Assembly. AssemblyHelper class can be easily extended with further functionalities as needed.

Implementation and examples are available both in C# and VB.Net languages.

Implementation

Below you can find implementation we use in Karmian Framework as Assembly helper. All members in AssemblyHelper class should be marked as static, so no instance is needed to invoke any. Class AssemblyHelper itself is marked as sealed as we do not want to allow any inheritance. If you need to add new functionality that supports the Assembly - it should be implemented in the class AssemblyHelper. This approach allows the system to prevent duplication of helpers that are responsible for similar actions.

AssemblyHelper class

using System;
using System.Reflection;
 
namespace Karmian.Framework.Helpers
{
  public sealed class AssemblyHelper
  {
    public static T[] GetCustomAttributes<T>(Assembly assembly) where T : Attribute
    {
      return GetCustomAttributes<T>(assembly, true);
    }
 
    public static T[] GetCustomAttributes<T>(Assembly assembly, bool inherit) where T : Attribute
    {
      if (assembly == null)
        throw new ArgumentNullException("assembly");
      var attributes = assembly.GetCustomAttributes(typeof (T), inherit) as T[];
      return attributes ?? new T[0];
    }
  }
}

Imports System.Reflection
 
Namespace Karmian.Framework.Helpers
  Public NotInheritable Class AssemblyHelper
    Public Shared Function GetCustomAttributes(Of T As Attribute)(assembly As Assembly) As T()
      Return GetCustomAttributes(Of T)(assembly, True)
    End Function
 
    Public Shared Function GetCustomAttributes(Of T As Attribute)(assembly As Assembly, inherit As Boolean) As T()
      If assembly Is Nothing Then
        Throw New ArgumentNullException("assembly")
      End If
      Dim attributes = TryCast(assembly.GetCustomAttributes(GetType(T), inherit), T())
      Return If(attributes, New T(-1) {})
    End Function
  End Class
End Namespace

LINQ lambda expressions in universal generic equality comparer

Submitted by Tomasz Paprocki on 21 September, 2010 - 19:18
in

Implementation

Below you can find implementation we use as universal equality comparer. Only lambda expressions as in LINQ queries are needed to measure items. Class LambdaComparer is generic, so you can use it on any type you want to.

LambdaComparer class

using System;
using System.Collections.Generic;
 
namespace Karmian.Framework.Helpers
{
    public class LambdaComparer<T> : IEqualityComparer<T>
    {
        public LambdaComparer(Func<T, T, bool> equals, Func<T, int> getHashCode)
        {
            _equals = equals;
            _getHashCode = getHashCode;
        }
 
        readonly Func<T, T, bool> _equals;
        public bool Equals(T x, T y)
        {
            return _equals(x, y);
        }
 
        readonly Func<T, int> _getHashCode;
        public int GetHashCode(T obj)
        {
            return _getHashCode(obj);
        }
    } 
}
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