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  • 拼接LINQ动态表达式

    using System;
    using System.Linq;
    using System.Linq.Expressions;
    
    public static class LinqBuilder
    {
        /// <summary>
        /// 默认True条件
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static Expression<Func<T, bool>> True<T>() { return f => true; }
    
        /// <summary>
        /// 默认False条件
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <returns></returns>
        public static Expression<Func<T, bool>> False<T>() { return f => false; }
    
        /// <summary>
        /// 拼接 OR 条件
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="exp"></param>
        /// <param name="condition"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> exp, Expression<Func<T, bool>> condition)
        {
            var inv = Expression.Invoke(condition, exp.Parameters.Cast<Expression>());
            return Expression.Lambda<Func<T, bool>>(Expression.Or(exp.Body, inv), exp.Parameters);
        }
    
        /// <summary>
        /// 拼接And条件
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="exp"></param>
        /// <param name="condition"></param>
        /// <returns></returns>
        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> exp, Expression<Func<T, bool>> condition)
        {
            var inv = Expression.Invoke(condition, exp.Parameters.Cast<Expression>());
            return Expression.Lambda<Func<T, bool>>(Expression.And(exp.Body, inv), exp.Parameters);
        }
    }
    
    public class Entity
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }
    
    public class Example
    {
        public Example()
        {
            var linq = LinqBuilder.True<Entity>();
            linq.And(p => p.Id == 30);
            Expression<Func<Entity, bool>> condition = linq.Or(p => p.Name == "");
        }
    }
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  • 原文地址:https://www.cnblogs.com/magic_evan/p/5664015.html
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