为什么 dynamic 在第一种情况下有效而在第二种情况下无效？

Question

这就过去了

        var badRequestObjectResult = new BadRequestObjectResult(new { ErrorMessage = "Hi" });
        dynamic response = badRequestObjectResult.Value;
        Assert.Equal("Hi", response.ErrorMessage);

虽然失败了

        dynamic response2 = ((BadRequestObjectResult)result).Value;//result is an IActionResult
        Assert.Equal("Hi", response2.ErrorMessage);

"Microsoft.CSharp.RuntimeBinder.RuntimeBinderException : 'object' does not contain a definition for 'ErrorMessage'"

Answer 1

您需要扩展您的答案以包含一个完整且可重现的示例。您所描述的内容按预期工作而没有错误，因此必须有一些介于两者之间的东西导致问题，例如自定义克隆或序列化正在改变 ObjectResult 的值背后的识别类型。

[Test]
public void TestDynamic()
{
    var response1 = new BadRequestObjectResult(new { Message = "Hi." });
    var response2 = buildResponse();

    dynamic value1 = response1.Value;
    dynamic value2 = ((BadRequestObjectResult)response2).Value;

    string message1 = value1.Message;
    string message2 = value2.Message;

    Assert.AreEqual(message1, message2);
}

private IActionResult buildResponse()
{
    return new BadRequestObjectResult(new { Message = "Hi." });
}

我重现错误的唯一方法是如果 buildResponse 返回：

return new BadRequestObjectResult(new object());

返回任何缺少消息的匿名类型或其他 class 属性会导致反映基础类型的消息。

为什么 dynamic 在第一种情况下有效而在第二种情况下无效？

Why does dynamic work in the first case but not in the second?

c#

dynamic

.net-core