使用属性或方法在C#中公开业务规则？

我正在编写一个类来封装一些业务规则,每个业务规则都由布尔值表示.该类将用于处理InfoPath表单,因此规则通过使用XPath操作在全局 XML数据结构中查找值来获取当前的程序状态.什么是最好的(最惯用的)方式来暴露这些规则给呼叫者 – 属性或公共方法？

使用属性调用

Rules rules = new Rules();
if ( rules.ProjectRequiresApproval ) {
    // get approval
} else {
    // skip approval
}

使用方法调用

Rules rules = new Rules();
if ( rules.ProjectRequiresApproval() ) {
    // get approval
} else {
    // skip approval
}

规则类将规则显示为属性

public class Rules() {
    private int _amount;
    private int threshold = 100;

    public Rules()  {
        _amount = someExpensiveXpathOperation;
    }

    // rule property
    public bool ProjectRequiresApproval {
        get { return _amount > threshold }
    }
}

规则类暴露规则作为方法

public class Rules() {
    private int _amount;
    private int threshold = 100;

    public Rules()  {
        _amount = someExpensiveXpathOperation;
    }

    // rule method
    public bool ProjectRequiresApproval() {
        return _amount > threshold;
    }
}

一个人的利弊是什么？