c# - Visual Studio 转义 Linq 语句的第三个条件

Question

Visual Studio c# 不会在输入条件之前检查 if 语句 userName 不应存在的第三个条件。我已经清理了解决方案清除了现金，但我仍然得到了忽略 Linq 语句的第三个条件的相同结果

 public async Task<ActionResult> Create( RegisterAsReqModel registerAsReqModel)
        {
            if (ModelState.IsValid)
            {

                //Create application user
                var user = new ApplicationUser { UserName = registerAsReqModel.UserName, Email = registerAsReqModel.EmailAddress};
                //assgin user to user type
                user.UserType = "Req";
                var result1 = db.Users.Where(m => m.UserName.Equals(registerAsReqModel.UserName)).FirstOrDefault();
                var result2 = db.Users.Where(m => m.Email.Equals(registerAsReqModel.EmailAddress)).FirstOrDefault();
                var result3 = from app in db.Users where app.Email.Equals(registerAsReqModel.EmailAddress) && app.UserType.Equals("Req") && app.UserName.Equals(registerAsReqModel.UserName) select app;
                 // 
                if (!result3.Any())
                {
                    UserManager.UserValidator = new UserValidator<ApplicationUser>(UserManager)
                    {
                        RequireUniqueEmail = false,

                    };
                    var result = await UserManager.CreateAsync(user, registerAsReqModel.Password);

                    if (result.Succeeded)
                    {
                        await UserManager.AddToRoleAsync(user.Id, "Req");
                        db.RegisterAsReqModels.Add(registerAsReqModel);
                        db.SaveChanges();

                        return RedirectToAction("Index");
                    }
                    AddErrors(result);
                }
                else if ((result1 != null) && (result2 !=null))
                {

                    ModelState.AddModelError("", "Email Address and UserName Both Exists!");
                } else if(db.Users.Where(m=>m.Email.Equals(registerAsReqModel.EmailAddress)).FirstOrDefault()!= null)
                {
                    ModelState.AddModelError("", "Email Address Exists!");

                }
                else
                {
                    ModelState.AddModelError("", "UserName  Exists!");
                }

            }

            return View(registerAsReqModel);
        }

型号分类:

public class RegisterAsReqModel
{
    [Key]
    public int Id { get; set; }
    [Required]
    public string FirstName { get; set; }
    [Required]
    public string LastName { get; set; }
    [Required]
    public string UserName { get; set; }
    [Required]
    [EmailAddress]
    public string EmailAddress { get; set; }
    [Required]
    [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
    [DataType(DataType.Password)]
    public string Password { get; set; }
}

Answer 1

result of ignoring the third condition of Linq statement

发生这种情况是因为 linq 中的第一个或第二个条件提出了错误。当多条件语句中有一个 false 时，解析器将忽略剩余的条件。根据应如何执行来更改条件将导致更有可能的结果。

此外，您正在使用 if 和 else if 条件相同。我建议也将它们组合起来，并在最后将错误显示为组合。

    if (ModelState.IsValid)
    {

        //Create application user
        var user = new ApplicationUser { UserName = registerAsReqModel.UserName, Email = registerAsReqModel.EmailAddress };
        //assgin user to user type
        user.UserType = "Req";
        var result1 = db.Users.Where(m => m.UserName.Equals(registerAsReqModel.UserName)).FirstOrDefault();
        var result2 = db.Users.Where(m => m.Email.Equals(registerAsReqModel.EmailAddress)).FirstOrDefault();

        var result3 = from app in db.Users where app.UserType.Equals("Req") && app.Email.Equals(registerAsReqModel.EmailAddress) && app.UserName.Equals(registerAsReqModel.UserName) select app;
        // 
        if (result3 == null)
        {
            UserManager.UserValidator = new UserValidator<ApplicationUser>(UserManager)
            {
                RequireUniqueEmail = false,

            };
            var result = await UserManager.CreateAsync(user, registerAsReqModel.Password);

            if (result.Succeeded)
            {
                await UserManager.AddToRoleAsync(user.Id, "Req");
                db.RegisterAsReqModels.Add(registerAsReqModel);
                db.SaveChanges();

                return RedirectToAction("Index");
            }
            AddErrors(result);
        }
        else if ((result1 != null) && (result2 != null))
        {
            StringBuilder sb = new StringBuilder();
            if (result2 != null)
            {
                sb.AppendLine("Email Address Exists!");

            }
            else
            {
                sb.AppendLine("UserName  Exists!");
            }
            ModelState.AddModelError("", sb.ToString());
        }
    }