無法從接口轉換爲

Question

類

我曾在我的方法的錯誤，當我嘗試添加到數據庫中我的接口，它給我的錯誤，

參數1：無法從「ForumSite.ActionsAndMethods轉換。 Registration.IRegistration'到'ForumSite.Models.User'。

這裏是IRegistration代碼：

using ForumSite.Models; 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 

namespace ForumSite.ActionsAndMethods.Registration 
{ 
public interface IRegistration 
{ 
    int UserId { get; } 
    string Email { get; } 
    string Password { get; } 
    string FirstName { get; } 
    string LastName { get; } 
    DateTime Birthday { get; } 
    DateTime DateCreated { get; set; } 
    string MobileNumber { get; } 
    string Address { get; } 
    int UserIsDeleted { get; set; } 
    int UserRoleId { get; set; } 
    UserRole UserRole { get; } 
} 
} 

而且這是在我的模型代碼：

namespace ForumSite.Models 
{ 
using ActionsAndMethods.Registration; 
using System; 
using System.Collections.Generic; 
using System.ComponentModel.DataAnnotations; 

public partial class User : IRegistration 
{ 
    public int UserId { get; set; } 
    [Display(Name = "Email Address")] 
    [Required(ErrorMessage = "This field required.")] 
    [RegularExpression(@"^([a-zA-Z0-9_\-\.]+)@([a-zA-Z]+)\.([a-zA-Z]{2,5})$", ErrorMessage = "Enter Valid Email Address")] 
    [StringLength(50, MinimumLength = 8, ErrorMessage = "8 to 50 characters only")] 
    public string Email { get; set; } 

    [Display(Name = "Password")] 
    [Required(ErrorMessage = "This field required.")] 
    [RegularExpression(@"^[a-zA-Z0-9]+$", ErrorMessage = "Alphanumeric characters only")] 
    [StringLength(50, MinimumLength = 8, ErrorMessage = "8 to 50 characters only")] 
    public string Password { get; set; } 

    [Display(Name = "Confirm Password")] 
    [Required(ErrorMessage = "This field required.")] 
    [RegularExpression(@"^[a-zA-Z0-9]+$", ErrorMessage = "Alphanumeric characters only")] 
    [StringLength(50, MinimumLength = 8, ErrorMessage = "8 to 50 characters only")] 
    public string PasswordConfirm { get; set; } 

    [Display(Name = "First Name")] 
    [Required(ErrorMessage = "This field required.")] 
    [RegularExpression(@"^[a-zA-Z\s]+$", ErrorMessage = "Letters Only.")] 
    public string FirstName { get; set; } 

    [Display(Name = "Last Name")] 
    [Required(ErrorMessage = "This field required.")] 
    [RegularExpression(@"^[a-zA-Z\s]+$", ErrorMessage = "Letters Only.")] 
    public string LastName { get; set; } 

    [Display(Name = "Birthday")] 
    [Required(ErrorMessage = "This field required.")] 
    public DateTime Birthday { get; set; } 
    public DateTime DateCreated { get; set; } 

    [Display(Name = "Mobile Number")] 
    [Required(ErrorMessage = "This field required.")] 
    [RegularExpression(@"^[0-9]+$", ErrorMessage = "Numeric input only.")] 
    public string MobileNumber { get; set; } 

    [Display(Name = "Address")] 
    [Required(ErrorMessage = "This field required.")] 
    public string Address { get; set; } 
    public int UserIsDeleted { get; set; } 
    public int UserRoleId { get; set; } 

    public UserRole UserRole { get; set; } 
} 
} 

最後，我的方法，將用戶添加到我的數據庫：

using ForumSite.ActionsAndMethods.Registration; 
using ForumSite.Models; 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 

namespace ForumSite.ActionsAndMethods 
{ 
public class RegisterAction : IRegistration 
{ 
    ForumDBEntities ent = new ForumDBEntities(); 
    public void Registration(IRegistration reg) 
    { 
     reg.DateCreated = DateTime.Now; 
     reg.UserRoleId = 1; 
     reg.UserIsDeleted = 0; 

     ent.Users.Add(reg); 
     ent.SaveChanges(); 
    } 

    string IRegistration.Address { get; } 
    int IRegistration.UserId { get; } 
    string IRegistration.Email { get; } 
    string IRegistration.Password { get; } 
    string IRegistration.FirstName { get; } 
    string IRegistration.LastName { get; } 
    DateTime IRegistration.Birthday { get; } 
    DateTime IRegistration.DateCreated { get; set; } 
    string IRegistration.MobileNumber { get; } 
    int IRegistration.UserIsDeleted { get; set; } 
    int IRegistration.UserRoleId { get; set; } 

    UserRole IRegistration.UserRole { get; } 
} 

} 

我不知道是什麼原因導致這個錯誤？

Answer 1

儘管每個User實現了IRegistration，但並非每個IRegistration實例都是User。

例如，您的RegisterAction也實施IRegistration。所以，如果你想做的事是可能的，你可以在理論上有這樣的代碼：

RegisterAction action = GetRegisterAction(); 

RegisterAction action2 = new RegisterAction(action); 

這意味着，當你來幹什麼：

ent.Users.Add(reg); 

它會失敗，因爲reg不是User 。

你可以解決它是這樣的：

var user = reg as User; 
if(user != null) 
{ 
    ent.Users.Add(user); 
} 

但實際上，因爲它似乎很奇怪，做這個你應該看看你的結構第一。

Answer 2

你還沒有告訴確切的是你在哪裏得到編譯錯誤，但我的猜測是它在Registration方法ent.Users.Add(reg)行。

要解決的編譯錯誤，你應該參數更改爲Registration方法從IRegistration到User：

public void Registration(User reg) 
{ 
    reg.DateCreated = DateTime.Now; 
    reg.UserRoleId = 1; 
    reg.UserIsDeleted = 0; 

    ent.Users.Add(reg); 
    ent.SaveChanges(); 
} 

然而，這可能進一步觸發另一個編譯錯誤了調用鏈，如果你試圖傳遞一個IRegistration而不是User到Registration方法。

雖然User可以（而且確實）實現IRegistration你不能假設任何實施IRegistration是User。如果你的代碼是基於這個假設，你將不得不解決這個問題來解決你的問題。