Yuebon.NetCore/Yuebon.Commons/Extensions/ExpressionExtensions.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using Newtonsoft.Json;

namespace Yuebon.Commons.Extensions
{
    /// <summary>
    /// 表达式树常用扩展方法
    /// </summary>
    public static class ExpressionExtensions
    {
        /// <summary>
        ///     取的  Expression<Func<T,TProperty>> predicate 表达式对应的属性名称
        ///         例如：c=>c.Value.Year 侧返回：Value.Year
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <typeparam name="TProperty"></typeparam>
        /// <param name="predicate"></param>
        /// <returns></returns>
        public static string GetPropertyName<T, TProperty>(this Expression<Func<T, TProperty>> predicate)
        {
            var expression = predicate.Body as MemberExpression;
            //return expression.Member.Name; //该属性只返回最后一个属性，因此采用下面方法返回。
            return expression.ToString().Substring(2);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="name"></param>
        /// <returns></returns>
        public static ParameterExpression CreateLambdaParam<T>(string name)
        {
            return Expression.Parameter(typeof(T), name);
        }

        /// <summary>
        /// 创建linq表达示的body部分
        /// </summary>
        public static Expression GenerateBody<T>(this ParameterExpression param, Filter filterObj)
        {
            PropertyInfo property = typeof(T).GetProperty(filterObj.Key);

            //组装左边
            Expression left = Expression.Property(param, property);
            //组装右边
            Expression right = null;

            if (property.PropertyType == typeof(int))
            {
                right = Expression.Constant(int.Parse(filterObj.Value));
            }
            else if (property.PropertyType == typeof(DateTime))
            {
                right = Expression.Constant(DateTime.Parse(filterObj.Value));
            }
            else if (property.PropertyType == typeof(string))