返工谓词构建器在创建动态where子句时更通用吗？

Question

我想抓住对象（例如：潜在客户）并让它根据订单映射到搜索过滤器。而不是if / then语句和下面的搜索参数。因此，lead_ID将映射到nvc [＆＃34; search_0＆＃34;]，lead_number将映射到nvc [＆＃34; search_1＆＃34;]等...

铅：

public class Fre_LeadSummaryDto
    {

        [DataMember]
        public string Lead_ID { get; set; }

        [DataMember]
        public string Lead_Number { get; set; }

         [DataMember]
        public string LeadSource { get; set; }

        [DataMember]
        public string MethodRecvd { get; set; }

        [DataMember]
        public string TotalLeadRecvd { get; set; }

        [DataMember] 
        public string TotalBalDueReturns { get; set; }

       [DataMember]
       public string DateLeadRecvd { get; set; }
    }

这是搜索过滤器和谓词设置：

 var predicate = PredicateBuilder.True<Fre_LeadSummaryDto>();

                if (!String.IsNullOrEmpty(nvc["sSearch_0"]))
                {
                    leadId = nvc["sSearch_0"];
                    predicate = predicate.And(i => i.Lead_ID.Equals(leadId));
                }

                if (!String.IsNullOrEmpty(nvc["sSearch_1"]))
                {
                    leadNumber = nvc["sSearch_1"];
                    predicate = predicate.And(i =>   i.Lead_Number.StartsWith(leadNumber));
                }

Where子句：

 leads = leads.Where(predicate);

谓词构建器：

/// <summary>   
    /// Enables the efficient, dynamic composition of query predicates.   
    /// </summary>   
    public static class PredicateBuilder
    {
        /// <summary>   
        /// Creates a predicate that evaluates to true.   
        /// </summary>   
        public static Expression<Func<T, bool>> True<T>() { return param => true; }

        /// <summary>   
        /// Creates a predicate that evaluates to false.   
        /// </summary>   
        public static Expression<Func<T, bool>> False<T>() { return param => false; }

        /// <summary>   
        /// Creates a predicate expression from the specified lambda expression.   
        /// </summary>   
        public static Expression<Func<T, bool>> Create<T>(Expression<Func<T, bool>> predicate) { return predicate; }

        /// <summary>   
        /// Combines the first predicate with the second using the logical "and".   
        /// </summary>   
        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>   
        /// Combines the first predicate with the second using the logical "or".   
        /// </summary>   
        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
        {
            return first.Compose(second, Expression.OrElse);
        }

        /// <summary>   
        /// Negates the predicate.   
        /// </summary>   
        public static Expression<Func<T, bool>> Not<T>(this Expression<Func<T, bool>> expression)
        {
            var negated = Expression.Not(expression.Body);
            return Expression.Lambda<Func<T, bool>>(negated, expression.Parameters);
        }

        /// <summary>   
        /// Combines the first expression with the second using the specified merge function.   
        /// </summary>   
        static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
        {
            // zip parameters (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 the parameters in the first   
            var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);

            // create a merged lambda expression with parameters from the first expression   
            return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
        }

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

            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);
            }
        }
    }