从c＃表达式获取对象的引用

问题描述

我有一个扩展通用方法

public static void AddError<TModel>(
    this ModelStateDictionary modelState,
    Expression<Func<TModel, object>> expression,
    string resourceKey,
    string defaultValue)
{
    // How can I get a reference to TModel object from expression here?
}

我需要从表达式获取对TModel对象的引用。
此方法由以下代码调用：

I need to get the reference to TModel object from expression.This method called by the following code:

ModelState.AddError<AccountLogOnModel>(
    x => x.Login, "resourceKey", "defaultValue")

推荐答案

您不能将其传递到方法中，而不能访问TModel对象。你传递的表达只是说从一个TModel拿这个属性。实际上并没有提供TModel来操作。所以，我将重构这样的代码：

You cannot get to the TModel object itself without passing it into the method. The expression you are passing in is only saying "take this property from a TModel". It isn't actually providing a TModel to operate on. So, I would refactor the code to something like this:

public static void AddError<TModel>(
    this ModelStateDictionary modelState,
    TModel item,
    Expression<Func<TModel, object>> expression,
    string resourceKey,
    string defaultValue)
{
    // TModel's instance is accessible through `item`.
}

然后你的电话代码看起来像这样：

Then your calling code would look something like this:

ModelState.AddError<AccountLogOnModel>(
    currentAccountLogOnModel, x => x.Login, "resourceKey", "defaultValue")

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