c# - 使用 Entity Framework 时出现 InvalidCastException

Question

我试图在对话类中保存用户列表，但在执行 POST 时收到 InvalidCastException。

这是我的用户类:

public class User
{
    [Key]
    [DataMember]
    public String Email { get; set; }

    [DataMember]
    public String Password { get; set; }

    [DataMember]
    public Boolean Admin { get; set; }

    public User(String email, String password, Boolean admin)
    {
        Email = email;
        Password = password;
        Admin = admin;
    }
}

这是我的 session 课:

[DataContract]
public class Conversation
{
    [Key]
    [DataMember]
    public string Key { get; set; }
    [DataMember]
    public string ConversationName { get; set; }
    [DataMember]
    public string Administrator { get; set; }
    [DataMember]
    [ForeignKey("Email")]
    public List<User> Members { get; set; }

    public Conversation(string key, string name, string admin, List<User> members)
    {
        Key = key;
        ConversationName = name;
        Administrator = admin;
        Members = members;
    }

    public Conversation()
    {

    }
}

这是对话 Controller :

发布:

    [HttpPost]
    public async Task<IHttpActionResult> PostConversation(Conversation convo)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        foreach (var user in convo.Members)
        {
            db.Entry(user).State = EntityState.Unchanged;
        }

        db.Conversations.Add(convo);
        await db.SaveChangesAsync();

        return CreatedAtRoute("DefaultApi", new { name = convo.Key }, convo);
    }

获取:

[HttpGet]
public IQueryable<Conversation> GetConversations()
{
    return db.Conversations;
}

编辑发表声明:

{
"Key": "123",
"ConversationName": "Test",
"Administrator": "Ken",
"Members": [{"Email": "y@12.com","Password" : "Passw-1", "Admin" : "true"},
            {"Email": "y@123.com","Password" : "Passw-1", "Admin" : "false"}]
}

我得到的错误是:

"ExceptionMessage": "Unable to cast object of type 'System.Collections.Generic.List`1[AcademicAssistant.Models.User]' to type 'AcademicAssistant.Models.User'.",

Answer 1

你的模型是错误的。由于您在 Conversation 之间存在 N:N 关系和 User你需要删除 ForeingKey Members 之前对话的属性, 你需要添加 ICollection<Conversation> Conversation User 类中的属性，或者进一步根据需要使用 FluentApi 配置关系