My ASP.NET MVC3 Notes(4)

04 – MVC Model

• Data Annotations

public class RegisterModel
{
    [Required]
    [Display(Name = "User name")]
    public string UserName { get; set; }

    [Required]
    [DataType(DataType.EmailAddress)]
    [Display(Name = "Email address")]
    public string Email { get; set; }

    [Required]
    [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
    [DataType(DataType.Password)]
    [Display(Name = "Password")]
    public string Password { get; set; }

    [DataType(DataType.Password)]
    // Dispaly Attribute is consumed by @Html.LableFor()
    [Display(Name = "Confirm password")]
    //Cross-Property comparison, new in MVC3
    [Compare("Password", ErrorMessage = "The password and confirmation password do not match.")]
    public string ConfirmPassword { get; set; }
}

The result:

• Custom Validation Attributes

Create my own Validation Class:

public class GreaterThanDateAttribute : ValidationAttribute // Needs to import [System.ComponentModel.DataAnnotations;]
{
    public GreaterThanDateAttribute(string otherPropertyName)
        :base("{0} must be greater than {1}") // This defines the ErrorMessage String
    {
        OtherPropertyName = otherPropertyName;
    }

    public override string FormatErrorMessage(string name)
    {
        return String.Format(ErrorMessage, name, OtherPropertyName); // "{0} must be greater than {1}"
    }
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        var otherPropertyInfo = validationContext.ObjectType.GetProperty(OtherPropertyName);
        var otherDate = (DateTime) otherPropertyInfo.GetValue(validationContext.ObjectInstance,null);
        var thisDate = (DateTime) value;
        if(thisDate<otherDate)
        {
            var message = FormatErrorMessage(validationContext.DisplayName);
            return new ValidationResult(message);
        }
        return null;
    }

    public string OtherPropertyName { get; set; }
}

In the Model TimeCard.cs, apply GreaterThanDate attribute to EndDate property

Test with invalid data:

• Remote Validation

Assign an action to perform the validation by applying [Remote] attribute to the property that needs to be validated

public class LogOnModel
{
    [Required]
    [Display(Name = "User name")]
    // 1.Action name; 2.Controller name; 3. Error message
    [Remote("ValidateUser","Account",ErrorMessage="Username is invalid")] 
    public string UserName { get; set; }

    [Required]
    [DataType(DataType.Password)]
    [Display(Name = "Password")]
    public string Password { get; set; }

    [Display(Name = "Remember me?")]
    public bool RememberMe { get; set; }
}

In Controller, add an action “ValidateUser”, validate the user name against database

public JsonResult ValidateUser(string username)
{
    //Validate user name against database
    var result = _db.ValidateUserName(username); 
    return Json(result, JsonRequestBehavior.AllowGet);
}

Validating in View: