泛型方法动态生成表达式树 Expression

        public string GetGridJSON(TraderInfo model)
        {
            IQueryable<TraderInfo> Temp = db.TraderInfo;
            if (model.LoginAccount != null)
            {
                Temp = Temp.Where(X => X.LoginAccount == model.LoginAccount);
            }
            if (model.ShopName != null)
            {
                Temp = Temp.Where(X => X.ShopName == model.ShopName);
            }
            return JsonConvert.SerializeObject(Temp.ToList(), Formatting.Indented, new JsonSerializerSettings() { DateFormatHandling = 0 });
        }

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
using System.Linq.Expressions;

namespace EF_DAL
{
    /// <summary>
    /// 动态生成 表达式树
    /// </summary>
    public class Custom_Expression
    {
        public delegate Expression delegate_Expression(Expression left, Expression right);
        private static BinaryExpression filter_Temp = Expression.Equal(Expression.Constant(1), Expression.Constant(1));

        /// <summary>
        /// 自定义Equal方法(允许value为null)，value为null 的时候，该查询条件 不会生成
        /// </summary>
        /// <typeparam name="T">实体数据类型</typeparam>
        /// <param name="StrArrPropertyName">以逗号分割的列名称</param>
        /// <param name="values">这些列对应的值</param>
        /// <returns>返回Lambda表达式，eg:where(Lambda)</returns>
        public Expression<Func<T, bool>> Custom_Equal<T>(string StrArrPropertyName, params object[] values)
        {
            return Custom_Expression_Function<T>(Equal_result, StrArrPropertyName, values);
        }

        private void Init()
        {
            filter_Temp = Expression.Equal(Expression.Constant(1), Expression.Constant(1));
        }

        public Expression<Func<T, bool>> Custom_Contain<T>(string StrArrPropertyName, params object[] values)
        {
            return Custom_Expression_Function<T>(Call_result, StrArrPropertyName, values);
        }

        private Expression Call_result(Expression left, Expression right)
        {
            return Expression.Call(left, typeof(string).GetMethod("Contains"), right);
        }

        private Expression Equal_result(Expression left, Expression right)
        {
            return Expression.Equal(left, right);
        }

        private Expression<Func<T, bool>> Custom_Expression_Function<T>(delegate_Expression del, string StrArrPropertyName, params object[] values)
        {
            Init();
            var PropertyName_arr = StrArrPropertyName.Split(‘,‘);
            var param = Expression.Parameter(typeof(T));
            for (int i = 0; i < PropertyName_arr.Length; i++)
            {
                if (values[i] == null) continue;
                string propertyName = PropertyName_arr[i].ToString();
                var value = values[i];
                Expression left = Expression.Property(param, typeof(T).GetProperty(propertyName));
                Expression right = Expression.Constant(value, value.GetType());
                Expression result = del(left, right);
                filter_Temp = Expression.And(filter_Temp, result);
            }
            return Expression.Lambda<Func<T, bool>>(filter_Temp, param);
        }
    }
}

 public string GetGridJSON(TraderInfo model)
        {
            EF_DAL.Custom_Expression CE = new EF_DAL.Custom_Expression();
            var rrr = db.TraderInfo.Where(CE.Custom_Equal<TraderInfo>("LoginAccount,ShopName", model.LoginAccount, model.ShopName)).ToList();
            return JsonConvert.SerializeObject(rrr, Formatting.Indented, new JsonSerializerSettings() { DateFormatHandling = 0 });
        }