'How to create custom validation attribute?

I am trying to create a custom validation attribute.

public class PhoneValidator : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        return new RegularExpressionAttribute(@"^[+0]\d+").IsValid(Convert.ToString(value).Trim());
    }
}

And I use this to use

[PhoneValidator]
public string PhoneNumber { get; private set; }

I copied it from a website, in theory this should work. But I couldn't make it work.

c++sharpdata-annotations


Solution 1:[1]

1-create a class for this

    [AttributeUsage(AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
    public class MobileValidationAttribute : ValidationAttribute
    {
        public MobileValidationAttribute(string errorMessage)
        {
            ErrorMessage = errorMessage;
        }

        public override bool IsValid(object value)
        {
            if (value == null) return false;
            return value.ToString().Length == 13;
        }
    }

2-create a model

    public class UserModel
    {
        [Display(Name ="Phone Number")]
        [MobileValidation("{0} is invalid")]
        [Required(AllowEmptyStrings =false,ErrorMessage ="{0} is required")]
        public string PhoneNumber { get; set; }
    }

3- in view use this code

@model TestAttribute.Models.UserModel
@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <div> 
        <form method="post" action="/Home/Index">
            @Html.LabelFor(a=>a.PhoneNumber)
            @Html.TextBoxFor(a=>a.PhoneNumber)
            @Html.ValidationMessageFor(a=>a.PhoneNumber)

            <br />
            <br />

            <button type="submit">Add</button>
        </form>
    </div>
</body>
</html>

4- and Controller

public class HomeController : Controller
    {
        public ActionResult Index()
        {
            return View(new UserModel());
        }

        [HttpPost]
        public ActionResult Index(UserModel model)
        {
            if (ModelState.IsValid)
            {
                return Content("Ok");
            }
            return View(model);
        }
    }

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Diako Hasani

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