Basic Logical Operations with LINQ Expressions

How to implement basic logical operations (AND, OR, NOT, XOR) with LINQ expressions:

 1  public   static   class  ExpressionExtensions
 2      {
 3           public   static  Expression < Func < T, Boolean >>  Or < T > ( this  Expression < Func < T, Boolean >>  expr, Expression < Func < T, Boolean >>  other)
 4          {
 5              InvocationExpression invokedExpr  =  Expression.Invoke(other, expr.Parameters.Cast < Expression > ());
 6               return  (Expression.Lambda < Func < T, Boolean >> (Expression.OrElse(expr.Body, invokedExpr), expr.Parameters));
 7          }
 8 
 9           public   static  Expression < Func < T, Boolean >>  Xor < T > ( this  Expression < Func < T, Boolean >>  expr, Expression < Func < T, Boolean >>  other)
10          {
11              InvocationExpression invokedExpr  =  Expression.Invoke(other, expr.Parameters.Cast < Expression > ());
12               return  (Expression.Lambda < Func < T, Boolean >> (Expression.ExclusiveOr(expr.Body, invokedExpr), expr.Parameters));
13          }
14 
15           public   static  Expression < Func < T, Boolean >>  Not < T > ( this  Expression < Func < T, Boolean >>  expr)
16          {
17               return  (Expression.Lambda < Func < T, Boolean >> (Expression.Not(expr.Body), expr.Parameters));
18          }
19 
20           public   static  Expression < Func < T, Boolean >>  And < T > ( this  Expression < Func < T, Boolean >>  expr, Expression < Func < T, Boolean >>  other)
21          {
22              InvocationExpression invokedExpr  =  Expression.Invoke(other, expr.Parameters.Cast < Expression > ());
23               return  (Expression.Lambda < Func < T, Boolean >> (Expression.AndAlso(expr.Body, invokedExpr), expr.Parameters));
24         }

25     }  

 

Usages: 

Expression<Func<int, bool>> isEven = i => (i % 2) == 0;

Expression<Func<int, bool>> isMultipleOfFive => i => (i % 5) == 0;

Expression<Func<int, bool>> evenOrMultipleOfFive = isEven.Or(isMultipleOfFive);

Expression<Func<int, bool>> isOdd = isEven.Not();

And so on.

转载于:https://www.cnblogs.com/Magicworks/archive/2011/04/10/2011700.html