LambdaToSql/FrameWork/LambdaHelpher.cs

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

namespace LambdaToSql.FrameWork
{
    public class LambdaHelpher<T>
    {
        /// <summary>
        /// 创建lambda表达式：p=>p.propertyName == propertyValue
        /// </summary>
        /// <typeparam name="T1"></typeparam>
        /// <param name="name"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public Expression<Func<T, bool>> Equal<T1>(string name, T1 value)
        {
            var parameter = Expression.Parameter(typeof(T), "ex");
            MemberExpression left = Expression.PropertyOrField(parameter, name);
            ConstantExpression right = Expression.Constant(value, typeof(T1));//创建常数
            //return Expression.Equal(left, right);
            return Expression.Lambda<Func<T, bool>>(Expression.Equal(left, right), parameter);
        }

        /// <summary>
        /// 创建lambda表达式：p=>p.propertyName != propertyValue
        /// </summary>
        /// <typeparam name="T1"></typeparam>
        /// <param name="name"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> NotEqual<T1>(string name, T1 value)
        {
            var parameter = Expression.Parameter(typeof(T), "ex");
            MemberExpression member = Expression.PropertyOrField(parameter, name);
            ConstantExpression constant = Expression.Constant(value, typeof(T1));//创建常数 
            return Expression.Lambda<Func<T, bool>>(Expression.NotEqual(member, constant), parameter);
        }

        /// <summary>
        /// 创建lambda表达式：p=>p.propertyName > propertyValue
        /// </summary>
        /// <typeparam name="T1"></typeparam>
        /// <param name="name"></param>
        /// <param name="value"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> GreaterThan<T1>(string name, T1 value)
        {
            var parameter = Expression.Parameter(typeof(T), "ex");
            MemberExpression member = Expression.PropertyOrField(parameter, name);
            ConstantExpression constant = Expression.Constant(value, typeof(T1));//创建常数 
            return Expression.Lambda<Func<T, bool>>(Expression.GreaterThan(member, constant), parameter);
        }

        /// <summary>
        /// 创建lambda表达式：p=>p.propertyName
        /// </summary>