C # uses enumerations as keys in dictionary

The enum type does not implement the IEquatable interface, and when an enum is used as a key in dictionary, boxing occurs and the efficiency is reduced.

You can avoid boxing operations on enumerations by using an overloaded version of dictionary that receives the iequalitycomparer<t> type.

A generic comparer implementation iequalitycomparer<t> is defined first.

1   Public classEnumcomparer<t>: iequalitycomparer<t>whereT:struct2     {3         #regioniequalitycomparer<t> generic interface implementation4 5          Public BOOLEquals (t first, T second)6         {7             varFirstparam = Expression.parameter (typeof(T)," First");8             varSecondparam = Expression.parameter (typeof(T),"Second");9             varEqualexpression =expression.equal (Firstparam, secondparam);Ten  One             returnExpression.lambda<func<t, T,BOOL>> A (Equalexpression, Firstparam, Secondparam). - Compile (). Invoke (first, second); -         } the  -          Public intGetHashCode (T instance) -         { -             varparameter = Expression.parameter (typeof(T),"instance"); +             varConvertexpression = Expression.convert (parameter,typeof(int)); -  +             returnExpression.lambda<func<t,int>> A (convertexpression, parameter). at Compile (). Invoke (instance); -         } -  -         #endregion -}

When you use an enumeration of type T as a key, you simply pass in a enumcomparer<t> instance in the constructor.

Reference: http://wayfarer.blog.51cto.com/1300239/280088

C # uses enumerations as keys in dictionary