[英]Why is my viewModel object returning null?
我有 2 个类,Message 和 User,并且我创建了一个包含这两个类的 viewModel:
public class User
{
[Key]
public int UserId { get; set; }
public string Username { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public ICollection<Message>? Messages { get; set; } = new Collection<Message>();
}
public class Message
{
[Key]
public int MessageId { get; set; }
public string MessageContent { get; set; }
public DateTime DateCreated { get; set; }
}
public class NewMessageViewModel
{
public Message Message { get; set; }
public User? Sender { get; set; }
public User? Receiver { get; set; }
}
但是,当我尝试通过 controller 传递 viewModel 并取回一些 json 时,它出现错误'System.NullReferenceException: 'Object reference not set to an instance of an object.'
我没有正确地通过某些东西,我知道,但对于我的生活,我可以看到有什么问题? 我太接近客观性了,所以有人可以指出我犯的愚蠢错误吗?
我的 controller 动作:
[Route("NewMessageViewModel")]
[HttpGet]
public NewMessageViewModel GetNewMessageViewModel()
{
NewMessageViewModel newmv = new NewMessageViewModel
{
Message = { MessageContent = "HelloWord", MessageId = 1, DateCreated = DateTime.Now},
Receiver = { UserId = 1, Messages = null, FirstName = "Andy", LastName = "Stav", Username = "AndyStav" },
Sender = { UserId = 2, Messages = null, FirstName = "Test", LastName = "Test", Username = "Test" }
};
return newmv;
}
您忘记初始化消息和用户 class:
NewMessageViewModel newmv = new NewMessageViewModel
{
Message = new Message { MessageContent = "HelloWord", MessageId = 1, DateCreated = DateTime.Now },
Receiver = new User { UserId = 1, Messages = null, FirstName = "Andy", LastName = "Stav", Username = "AndyStav" },
Sender = new User { UserId = 2, Messages = null, FirstName = "Test", LastName = "Test", Username = "Test" }
};
return newmv;
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