表示或者-变量'；a'；类型'；预约'；引用自scope''；，但是它没有被定义

本文关键字：定义 scope 引用 变量 或者 类型 表示 预约 | 更新日期: 2023-09-27 17:59:51

我试图连接两个表达式，但在Compile方法的标题中提到了错误：

 Expression<Func<Appointment, bool>> week1 = StartDateIsBetween(lastMonday, nextSunday);
 Expression<Func<Appointment, bool>> week2 = EndDateIsBetween(lastMonday, nextSunday);
 BinaryExpression weekOr = Expression.Or(week1.Body, week2.Body);
 Func<Appointment, bool> week = Expression.Lambda<Func<Appointment, bool>>(weekOr, week1.Parameters.Single()).Compile();

创建表达式的另外两种方法：

 private Expression<Func<Appointment, bool>> StartDateIsBetween(DateTime beginningDate, DateTime endDate)
    {
        return a => a.StartDate >= beginningDate && a.StartDate <= endDate;
    }
    private Expression<Func<Appointment, bool>> EndDateIsBetween(DateTime beginningDate, DateTime endDate)
    {
        return a => a.EndDate >= beginningDate && a.EndDate <= endDate;
    }

知道如何修复这个错误吗？我是表达式树的初学者：/

表示或者-变量'；a'；类型'；预约'；引用自scope''；，但是它没有被定义

week1和week2具有不同的参数，因为它们是单独创建的。最简单的方法是在现有表达式上使用ExpressionInvoke，并使用新的ExpressionParameter实例：

var param = Expression.Parameter(typeof(Appointment));
var weekOr = Expression.Or(Expression.Invoke(week1, param), Expression.Invoke(week2, param));
var week = Expression.Lambda<Func<Appointment, bool>>(weekOr, param).Compile();
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