To implement custom validation in C# ASP.NET MVC4, it needs
to inherit “ValidationAttribute” class and overwrite “IsValid” method in your
class. For this you need to add namespace System.ComponentModel.DataAnnotations.
Here, I am creating a class for my custom password
attributes and its minimum length should be of 5 chars and maximum length should be of 10 chars. I have
initialized the values in its constructor and defined the code logic in
overridden method “IsValid”.
public class PasswordAttribute : ValidationAttribute
{
int
MinLength;
int
MaxLength;
public PasswordAttribute(int minLength, int
maxLength)
{
this.MinLength = minLength;
this.MaxLength = maxLength;
}
public override bool
IsValid(object value)
{
// TODO:
if (condition_satisfied)
return true;
else
return false;
}
}
Use the class to validate password value:
public class
SetUserPassword
{
[Required(ErrorMessage = "Please
enter a password.", AllowEmptyStrings = false)]
[Password(5, 10, ErrorMessage = "Please enter 5-10 digits password.")]
public string
Password { get; set;
}
}
For ActionResult attribute, you must inherit ActionFilterAttribute class and override respective base method, as per your need. ActionFilterAttribute resides in namespace System.Web.Mvc. Here, I am overriding OnActionExecuting method that executes while execution of an action.
public class CheckUserSessionAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
HttpCookie ck = HttpContext.Current.Request.Cookies["user"];
if (ck == null || string.IsNullOrEmpty(ck.Value))
filterContext.Result = new RedirectResult("home/login");
}
}
[HttpGet]
[CheckUserSession]
public ActionResult Index()
{
return View();
}
ASP.Net MVC 4 provides four
types of validations:
1. Required – To check for required
field.
2. Range- To check for lower and
upper limits.
3. Regular expression- To check for
an expression.
4. Custom validation- User defined
validation.
MVC4 does not provide Compare
validation as in previous ASPX web forms. If you wish to use compare
validation, either you may need to use the available DLL or go for custom
validation.
