使用表达式定义验证规则 [英] Using expressions to define validation rules

问题描述

我想创建一个通用的验证类，所以我可以这样做：

I want to create a generic validation class, so I can do something like:

Validation v = new Validation();
v.AddRequired(x => this.Name);
v.AddRange(x => x.this.Age, 5, 65);

我不确定如何编写方法定义并进行评估？

I'm unsure as to how to write the method definition and make the evaluation?

其中 AddRequired 将采用字符串和 AddRange 将采用数字类型（ int ，主要是 double ， decimal 等）

Where AddRequired would take a string and AddRange would take a numeric type (int, primarily but also double, decimal, etc)

推荐答案

一种方法是：

class ObjectToBeValidated {
   public string Name { get; set; }
   public int Age { get; set; }
}

class Validation {
    private List<Expression<Func<ObjectToBeValidated, bool>>> requiredExpressions;
    private List<Expression<Func<ObjectToBeValidated, bool>>> rangeExpressions;

    public void AddRequired(Expression<Func<ObjectToBeValidated, string>> expression)
    {
        Expression<Func<ObjectToBeValidated, bool>> checkRequired = (p => !string.IsNullOrEmpty(expression.Compile().Invoke(p)));
        requiredExpressions.Add(checkRequired);
    }

    public void AddRange(Expression<Func<ObjectToBeValidated, int>> expression, int min, int max)
    {
        Func<ObjectToBeValidated, int> compiledFunc = expression.Compile();
        Expression<Func<ObjectToBeValidated, bool>> checkRange = (p => compiledFunc.Invoke(p) >= min && compiledFunc.Invoke(p) < max);
        rangeExpressions.Add(checkRange);
    }
}

这只会将您的条件存储在列表与LT; T> 的。
然后，您必须在验证类中添加一个方法来评估表达式：

This would just store your conditions in List<T>'s. You then would have to add a method to your Validation class to evaluate the expressions:

public bool IsValid(ObjectToBeValidated testObject)
    {
        return requiredExpressions.All(p => p.Compile().Invoke(testObject))
            && rangeExpressions.All(p => p.Compile().Invoke(testObject));
    }

然后使用如下：

validator.AddRequired(p => p.Name);
validator.AddRange(p => p.Age, 6, 15);

var myObject = new ObjectToBeValidated();
var result = validator.IsValid(myObject);

这篇关于使用表达式定义验证规则的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！