public static class PredicateExtensions    {        public static Expression
     
      
       > True
       
        () { return f => true; }        public static Expression
        
         
          > False
          
           () { return f => false; } public static Expression
           
            
             > Or
             
              (this Expression
              
               
                > expression1, Expression
                
                 
                  > expression2) { var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast
                  
                   ()); return Expression.Lambda
                   
                    
                     >(Expression.Or(expression1.Body, invokedExpression), expression1.Parameters); } public static Expression
                     
                      
                       > And
                       
                        (this Expression
                        
                         
                          > expression1, Expression
                          
                           
                            > expression2) { var invokedExpression = Expression.Invoke(expression2, expression1.Parameters.Cast
                            
                             ()); return Expression.Lambda
                             
                              
                               >(Expression.And(expression1.Body, invokedExpression), expression1.Parameters); } public static Expression
                               
                                
                                 > Not
                                 
                                  (this Expression
                                  
                                   
                                    > expression) { var negated = Expression.Not(expression.Body); return Expression.Lambda
                                    
                                     
                                      >(negated, expression.Parameters); } }
                                     
                                    
                                   
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

用法： 

Expression
     
      
       > expression = PredicateExtensions.True
       
        ();expression = expression.And(x=> x.Name == "ABC");expression = expression.Or(x=> x.Name == "XYZ");expression = expression.Not();