using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
namespace OSS.ETS.OMS.Common
{
/// <summary>
/// 构造函数使用True时:单个AND有效,多个AND有效;单个OR无效,多个OR无效;混合时写在AND后的OR有效
/// 构造函数使用False时:单个AND无效,多个AND无效;单个OR有效,多个OR有效;混合时写在OR后面的AND有效
/// </summary>
/// 创建者:王宇
/// 创建日期:9/1/2014 10:38 AM
/// 修改者:
/// 修改时间:
/// ------------------------------------
public static class PredicateExtensions
{
public static Expression<Func<T, bool>> True<T>() { return f => true; }
public static Expression<Func<T, bool>> False<T>() { return f => false; }
/// <summary>
/// lambda表达式Or
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expression1">The expression1.</param>
/// <param name="expression2">The expression2.</param>
/// <returns></returns>
/// 创建者:王宇
/// 创建日期:9/1/2014 10:32 AM
/// 修改者:
/// 修改时间:
/// ------------------------------------
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expression1, Expression<Func<T, bool>> expression2)
{
var invokedExpression = Expression.Invoke(expression2, expression1.Parameters);
return Expression.Lambda<Func<T, bool>>(Expression.Or(expression1.Body, invokedExpression), expression1.Parameters);
}
/// <summary>
/// lambda表达式And
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="expression1">The expression1.</param>
/// <param name="expression2">The expression2.</param>
/// <returns></returns>
/// 创建者:王宇
/// 创建日期:9/1/2014 10:30 AM
/// 修改者:
/// 修改时间:
/// ------------------------------------
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expression1, Expression<Func<T, bool>> expression2)
{
var invokedExpression = Expression.Invoke(expression2, expression1.Parameters);
return Expression.Lambda<Func<T, bool>>(Expression.And(expression1.Body, invokedExpression), expression1.Parameters);
}
/// <summary>
/// 排除重复数据.
/// </summary>
/// <typeparam name="TSource"></typeparam>
/// <typeparam name="TKey"></typeparam>
/// <param name="source">集合.</param>
/// <param name="keySelector">排重表达式.</param>
/// <returns></returns>
/// 创建者:王宇
/// 创建日期:9/1/2014 10:28 AM
/// 修改者:
/// 修改时间:
/// ------------------------------------
public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
var seenKeys = new HashSet<TKey>();
return source.Where(element => seenKeys.Add(keySelector(element)));
}
}
}
本站仅提供存储服务,所有内容均由用户发布,如发现有害或侵权内容,请
点击举报。