LinQ的动态多条件查询

/// <summary>
    /// 重点
    /// 构造函数使用True时：单个AND有效，多个AND有效；单个OR无效，多个OR无效；混合时写在AND后的OR有效
    /// 构造函数使用False时：单个AND无效，多个AND无效；单个OR有效，多个OR有效；混合时写在OR后面的AND有效
    /// </summary>
    public static class ExpressionExtensions
    {
        /// <summary>
        ///     以特定的条件运行组合两个Expression表达式
        /// </summary>
        /// <typeparam name="T">表达式的主实体类型</typeparam>
        /// <param name="first">第一个Expression表达式</param>
        /// <param name="second">要组合的Expression表达式</param>
        /// <param name="merge">组合条件运算方式</param>
        /// <returns>组合后的表达式</returns>
        public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second,
            Func<Expression, Expression, Expression> merge)
        {
            var map =
                first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);
            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);
            return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
        }

        /// <summary>
        ///     以 Expression.AndAlso 组合两个Expression表达式
        /// </summary>
        /// <typeparam name="T">表达式的主实体类型</typeparam>
        /// <param name="first">第一个Expression表达式</param>
        /// <param name="second">要组合的Expression表达式</param>
        /// <returns>组合后的表达式</returns>
        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first,
            Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.AndAlso);
        }
        /// <summary>
        /// 传入条件之间为OR查询
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="source"></param>
        /// <param name="predicates"></param>
        /// <returns></returns>
        public static IQueryable<T> WhereOR<T>(this IQueryable<T> source, params Expression<Func<T, bool>>[] predicates)
        {
            if (source == null) throw new ArgumentNullException("source");
            if (predicates == null) throw new ArgumentNullException("predicates");
            if (predicates.Length == 0) return source.Where(x => false); // no matches!
            if (predicates.Length == 1) return source.Where(predicates[0]); // simple

            var param = Expression.Parameter(typeof(T), "x");
            Expression body = Expression.Invoke(predicates[0], param);
            for (int i = 1; i < predicates.Length; i++)
            {
                body = Expression.OrElse(body, Expression.Invoke(predicates[i], param));
            }
            var lambda = Expression.Lambda<Func<T, bool>>(body, param);
            return source.Where(lambda);
        }
        /// <summary>
        ///     以 Expression.OrElse 组合两个Expression表达式
        /// </summary>
        /// <typeparam name="T">表达式的主实体类型</typeparam>
        /// <param name="first">第一个Expression表达式</param>
        /// <param name="second">要组合的Expression表达式</param>
        /// <returns>组合后的表达式</returns>
        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first,
            Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.Or);
        }
        public static Expression<Func<T, bool>> OrElse<T>(this Expression<Func<T, bool>> first,
            Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.OrElse);
        }

        private class ParameterRebinder : ExpressionVisitor
        {
            private readonly Dictionary<ParameterExpression, ParameterExpression> _map;

            private ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
            {
                _map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
            }

            public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map,
                Expression exp)
            {
                return new ParameterRebinder(map).Visit(exp);
            }

            protected override Expression VisitParameter(ParameterExpression node)
            {
                ParameterExpression replacement;
                if (_map.TryGetValue(node, out replacement))
                    node = replacement;
                return base.VisitParameter(node);
            }
        }
    }

使用

actionPlanList.Add(actionPlanModel); 
 Expression<Func<ActionPlanModel, bool>> ex = t => false;
if (projectNames.Count>0)
            {
                
                foreach (var projectName in projectNames)
                {
                    ex = ex.Or(s => s.ProjectName==projectName);
                }
                
            }
            if (coachAccountNames.Count>0)
            {

                foreach (var coachAccountName in coachAccountNames)
                {
                    ex = ex.Or(s => s.CoachName==coachAccountName);
                }
            }
            if (DealerNameCNs.Count>0)
            {
                foreach (var DealerNameCN in DealerNameCNs)
                {
                    ex = ex.Or(s => s.DealerNameCN==DealerNameCN);
                }
               
            }
          //And在后面
            if (!string.IsNullOrEmpty(projectYear))
            {
                ex = ex.And(s => s.ProjectYear.Equals(projectYear));
            }
             actionPlanListNew = actionPlanList.Where(ex.Compile()).ToList();