将MemberExpression应用于对象以检索属性值 [英] Apply MemberExpression to an object to retrieve Property value

问题描述

我正在尝试编写一个接受MemberExpression和对象并返回成员表达式中定义的Property值的泛型函数.

I am trying to write a generic function that takes a MemberExpression and an object and returns the value of the Property defined in the member expression.

这是获取属性名称的代码示例.

Here's an example of the code to get the Property name.

public static TProperty GetPropertyName<TModel, TProperty>(Expression<Func<TModel, TProperty>> expression, TModel model)
{
    if (expression.Body is MemberExpression)
    {
        return ((MemberExpression)expression.Body).Member.Name;
    }
    else
    {
        var op = ((UnaryExpression)expression.Body).Operand;
        return ((MemberExpression)op).Member.Name;
    }
}

但是我想从模型中检索属性的值:

But I want to retrieve the value of the property from the model:

public static string GetPropertyValue<TModel, TProperty>(Expression<Func<TModel, TProperty>> expression, TModel model)
{
    if (expression.Body is MemberExpression)
    {
        // how do I apply the expression.Body to get the value of the property from model??

    }
    else
    {
        var op = ((UnaryExpression)expression.Body).Operand;
        return ((MemberExpression)op).Member.Name;
    }
}

我调用此函数的方式是:

The way I call this function is:

GetPropertyValue<ObjectModel,bool>(m => m.somebool, m);

推荐答案

MemberExpression指的是此外，交换参数更为自然(第一个是model，第二个是表达式).副作用是，这允许编译器推断类型参数:

Besides, it is more natural to swap parameters (first is model, second is expression). As a side effect, this allows compiler to infer type arguments:

var bar = MemberExpressionHelper.GetPropertyValue(foo, _ => _.Bar);

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