EnumDataTypeAttribute.cs

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using System.Globalization;
 
namespace System.ComponentModel.DataAnnotations;
 
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public sealed class EnumDataTypeAttribute : DataTypeAttribute
{
    public Type EnumType { get; }
 
    public EnumDataTypeAttribute(Type enumType)
        : base("Enumeration")
    {
        EnumType = enumType;
    }
 
    public override bool IsValid(object? value)
    {
        if (EnumType == null)
        {
            throw new InvalidOperationException(System.SR.EnumDataTypeAttribute_TypeCannotBeNull);
        }
        if (!EnumType.IsEnum)
        {
            throw new InvalidOperationException(System.SR.Format(System.SR.EnumDataTypeAttribute_TypeNeedsToBeAnEnum, EnumType.FullName));
        }
        if (value == null)
        {
            return true;
        }
        string text = value as string;
        if (text != null && text.Length == 0)
        {
            return true;
        }
        Type type = value.GetType();
        if (type.IsEnum && EnumType != type)
        {
            return false;
        }
        if (!type.IsValueType && type != typeof(string))
        {
            return false;
        }
        if (type == typeof(bool) || type == typeof(float) || type == typeof(double) || type == typeof(decimal) || type == typeof(char))
        {
            return false;
        }
        object obj;
        if (type.IsEnum)
        {
            obj = value;
        }
        else
        {
            try
            {
                obj = ((text != null) ? Enum.Parse(EnumType, text, ignoreCase: false) : Enum.ToObject(EnumType, value));
            }
            catch (ArgumentException)
            {
                return false;
            }
        }
        if (IsEnumTypeInFlagsMode(EnumType))
        {
            string underlyingTypeValueString = GetUnderlyingTypeValueString(EnumType, obj);
            string value2 = obj.ToString();
            return !underlyingTypeValueString.Equals(value2);
        }
        return Enum.IsDefined(EnumType, obj);
    }
 
    private static bool IsEnumTypeInFlagsMode(Type enumType)
    {
        return enumType.IsDefined(typeof(FlagsAttribute), inherit: false);
    }
 
    private static string GetUnderlyingTypeValueString(Type enumType, object enumValue)
    {
        return Convert.ChangeType(enumValue, Enum.GetUnderlyingType(enumType), CultureInfo.InvariantCulture).ToString();
    }
}