using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
namespace Project.Service.Infrastructure
{
public static class PredicateBuilder
{
///
/// 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
///
///
public static Expression<Func<T, bool>> True
///
/// 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
///
///
public static Expression<Func<T, bool>> False
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
Expression<Func<T, bool>> expr2)
{
var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>
(Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
}
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
Expression<Func<T, bool>> expr2)
{
var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
return Expression.Lambda<Func<T, bool>>
(Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
}
}
}