Linq To Entity多条件or查询处理

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1.多条件OR使用实例：

//学费if (string.IsNullOrEmpty(tuition) == false && tuition != "0"){    Expression<Func<School, bool>> orQuery = q => false;    foreach (var item in tuitionID)    {        Tuition tui = Tuition.GetMode(item);        orQuery = orQuery.Or(q => q.TuitionFee >= tui.MinValue && q.TuitionFee < tui.MaxValue);    }    query = query.Where(orQuery);}

2.添加扩展方法

    public static class Utility    {        public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)        {            // build parameter map (from parameters of second to parameters of first)            var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);            // replace parameters in the second lambda expression with parameters from the first            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);            // apply composition of lambda expression bodies to parameters from the first expression            return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);        }        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)        {            return first.Compose(second, Expression.And);        }        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 class ParameterRebinder : ExpressionVisitor    {        private readonly Dictionary<ParameterExpression, ParameterExpression> map;        public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)        {            this.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 p)        {            ParameterExpression replacement;            if (map.TryGetValue(p, out replacement))            {                p = replacement;            }            return base.VisitParameter(p);        }    }

更多参考：

https://blogs.msdn.microsoft.com/meek/2008/05/02/linq-to-entities-combining-predicates/

http://www.cnblogs.com/blackice/archive/2013/01/08/2851424.html

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