@Html.DropDownListFor(model => model.AccountType, new SelectList(Enum.GetNames(typeof(Enums.AccountType))))

public enum AccountType : byte
{
   مدیر = 0,
   کاربر_حقیقی = 1,
   کاربر_حقوقی = 2,
}

namespace MvcApplication1.Models
{
    [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
    public abstract class PropertyBindAttribute : Attribute
    {
        public abstract bool BindProperty(ControllerContext controllerContext,
        ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor);
    }

    public class ExtendedModelBinder : DefaultModelBinder
    {
        protected override void BindProperty(ControllerContext controllerContext,
            ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor)
        {
            if (propertyDescriptor.Attributes.OfType<PropertyBindAttribute>().Any())
            {
                var modelBindAttr = propertyDescriptor.Attributes.OfType<PropertyBindAttribute>().FirstOrDefault();

                if (modelBindAttr.BindProperty(controllerContext, bindingContext, propertyDescriptor))
                    return;
            }

            base.BindProperty(controllerContext, bindingContext, propertyDescriptor);
        }
    }
}

    public class AccountTypeBindAttribute : PropertyBindAttribute
    {
        public override bool BindProperty(ControllerContext controllerContext,
            ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor)
        {
            if (propertyDescriptor.PropertyType == typeof(byte))
            {
                HttpRequestBase request = controllerContext.HttpContext.Request;

                byte accountType = (byte)Enum.Parse(typeof(Enums.AccountType), request.Form["AccountType"]);
                propertyDescriptor.SetValue(bindingContext.Model, accountType);

                return true;
            }
            return false;
        }
    }  

[AccountTypeBindAttribute]
public byte AccountType { get; set; }

ModelBinders.Binders.DefaultBinder = new ExtendedModelBinder();

   The field نوع کاربر : must be a number.     

@Html.DropDownListFor(model => model.AccountType, new SelectList(Enum.GetNames(typeof(Enums.AccountType))),new Dictionary<string, object>() {{ "data-val", "false" }})

[ServiceContract]
public interface IService1                       
{
    [OperationContract]                                 
    string GetData(int value);
    [OperationContract]
    CompositeType GetDataUsingDataContract(CompositeType composite);
}
...
public class Service1 : IService1                         
{
    public string GetData(int value)
    {
        return string.Format("You entered: {0}", value);
    }

    public CompositeType GetDataUsingDataContract(CompositeType composite)
    {
        if (composite == null)
        {
            throw new ArgumentNullException("composite");
        }
        if (composite.BoolValue)
        {
            composite.StringValue += "Suffix";
        }
        return composite;
    }
}

• درگاه‌ها (اجباری)
  
• HttpContext (اجباری)
  
• پایگاه داده (اجباری)
  
• پیام‌ها (اختیاری)
  

PM> Install-Package foolproof

public class Triangle
{
    private int _height;
    private int _baseLength;

    public int Height
    {
        get { return _height; }

        set
        {
            if (value < 1 || value > 100)
            {
                // تولید خطا
            }

            _height = value;
        }
    }

    public int BaseLength
    {
        get { return _baseLength; }

        set
        {
            if (value < 1 || value > 100)
            {
                // تولید خطا
            }

            _baseLength = value;
        }
    }

    public double Area
    {
        get { return _height * _baseLength * 0.5; }
    }
}

public Triangle()
{
    _height = _baseLength = 1;
}

Triangle triangle = new Triangle();
 
Console.WriteLine(triangle.Height);
Console.WriteLine(triangle.BaseLength);
Console.WriteLine(triangle.Area);

public Triangle(int height, int baseLength)
{
    Height = height;
    BaseLength = baseLength;
}

Triangle triangle = new Triangle(5, 8);
 
Console.WriteLine(triangle.Height);
Console.WriteLine(triangle.BaseLength);
Console.WriteLine(triangle.Area);

using System.Diagnostics.CodeAnalysis;

namespace CS11Tests;

public class StringSyntaxAttributeTests
{
    public static void Test()
    {
        RegexTest("");
        DateTest("");
    }

    private static void RegexTest([StringSyntax(StringSyntaxAttribute.Regex)] string regex)
    {
    }

    private static void DateTest([StringSyntax(StringSyntaxAttribute.DateTimeFormat)] string dateTime)
    {
    }
}

#if !NET7_0_OR_GREATER

namespace System.Diagnostics.CodeAnalysis
{
  /// <summary>Specifies the syntax used in a string.</summary>
  [AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
  public sealed class StringSyntaxAttribute : Attribute
  {
    /// <summary>The syntax identifier for strings containing composite formats for string formatting.</summary>
    public const string CompositeFormat = "CompositeFormat";
    /// <summary>The syntax identifier for strings containing date format specifiers.</summary>
    public const string DateOnlyFormat = "DateOnlyFormat";
    /// <summary>The syntax identifier for strings containing date and time format specifiers.</summary>
    public const string DateTimeFormat = "DateTimeFormat";
    /// <summary>The syntax identifier for strings containing <see cref="T:System.Enum" /> format specifiers.</summary>
    public const string EnumFormat = "EnumFormat";
    /// <summary>The syntax identifier for strings containing <see cref="T:System.Guid" /> format specifiers.</summary>
    public const string GuidFormat = "GuidFormat";
    /// <summary>The syntax identifier for strings containing JavaScript Object Notation (JSON).</summary>
    public const string Json = "Json";
    /// <summary>The syntax identifier for strings containing numeric format specifiers.</summary>
    public const string NumericFormat = "NumericFormat";
    /// <summary>The syntax identifier for strings containing regular expressions.</summary>
    public const string Regex = "Regex";
    /// <summary>The syntax identifier for strings containing time format specifiers.</summary>
    public const string TimeOnlyFormat = "TimeOnlyFormat";
    /// <summary>The syntax identifier for strings containing <see cref="T:System.TimeSpan" /> format specifiers.</summary>
    public const string TimeSpanFormat = "TimeSpanFormat";
    /// <summary>The syntax identifier for strings containing URIs.</summary>
    public const string Uri = "Uri";
    /// <summary>The syntax identifier for strings containing XML.</summary>
    public const string Xml = "Xml";

    /// <summary>Initializes the <see cref="T:System.Diagnostics.CodeAnalysis.StringSyntaxAttribute" /> with the identifier of the syntax used.</summary>
    /// <param name="syntax">The syntax identifier.</param>
    public StringSyntaxAttribute(string syntax)
    {
      this.Syntax = syntax;
      this.Arguments = Array.Empty<object>();
    }

    /// <summary>Initializes the <see cref="T:System.Diagnostics.CodeAnalysis.StringSyntaxAttribute" /> with the identifier of the syntax used.</summary>
    /// <param name="syntax">The syntax identifier.</param>
    /// <param name="arguments">Optional arguments associated with the specific syntax employed.</param>
    public StringSyntaxAttribute(string syntax, params object?[] arguments)
    {
      this.Syntax = syntax;
      this.Arguments = arguments;
    }

    /// <summary>Gets the identifier of the syntax used.</summary>
    public string Syntax { get; }

    /// <summary>Gets the optional arguments associated with the specific syntax employed.</summary>
    public object?[] Arguments { get; }
  }
}

#endif