C# 自定义特性属性 限制自定义字段 数据

不知道怎么表达这个东西，先记录一下吧，如果你们有好的想法可以联系我，共同进步

/// <summary>
        /// 自定义属性帮助类
        /// </summary>
        public class AttributeHelper
        {
            /// <summary>
            /// 获取字符串字节长度
            /// </summary>
            /// <param name="str"></param>
            /// <returns></returns>
            public static int StringToByteLength(string str)
            {
                //使用Unicode编码的方式将字符串转换为字节数组,它将所有字符串(包括英文中文)全部以2个字节存储
                byte[] bytestr = System.Text.Encoding.UTF8.GetBytes(str);
                int j = 0;
                for (int i = 0; i < bytestr.GetLength(0); i++)
                {
                    //取余2是因为字节数组中所有的双数下标的元素都是unicode字符的第一个字节
                    if (i % 2 == 0)
                    {
                        j++;
                    }
                    else
                    {
                        //单数下标都是字符的第2个字节,如果一个字符第2个字节为0,则代表该Unicode字符是英文字符,否则为中文字符
                        if (bytestr[i] > 0)
                        {
                            j++;
                        }
                    }
                }
                return j;
            }
            /// <summary>
            /// 验证字段属性
            /// </summary>
            public void Validate()
            {
                ValidationContext context = new ValidationContext(this, serviceProvider: null, items: null);
                List<ValidationResult> results = new List<ValidationResult>();
                bool isValid = Validator.TryValidateObject(this, context, results, true);

                if (isValid == false)
                {
                    StringBuilder sbrErrors = new StringBuilder();
                    foreach (var validationResult in results)
                    {
                        sbrErrors.AppendLine(validationResult.ErrorMessage);
                    }
                    throw new ValidationException(sbrErrors.ToString());
                }
            }

            /// <summary>
            /// 判断字符串字节长度
            /// </summary>
            public class IsByteLength : ValidationAttribute
            {
                public IsByteLength(string errorMsg, int len)
                {
                    this.ErrorMsg = errorMsg;
                    this.Len = len;
                }
                public string ErrorMsg { get; private set; }
                public int Len { get; private set; }
                protected override ValidationResult IsValid(object value, ValidationContext validationContext)
                {
                    if (value.GetType().Equals(typeof(string)))
                    {
                        if (StringToByteLength(value.ToString()) > Len)
                        {
                            var error = new ValidationResult(ErrorMsg);
                            return error;
                        }
                    }
                    return null;
                }
            }
            public static string ObjToString( object thisValue)
            {
                if (thisValue != null) return thisValue.ToString().Trim();
                return "";
            }

            public class IsFieldVereist : ValidationAttribute
            {
                public string ErrorMsg { get; private set; }
                public string TypeName { get; private set; }
                public IsFieldVereist(string errorMsg, string typeName="")
                {
                    this.ErrorMsg = errorMsg;
                    this.TypeName = typeName;
                }
                protected override ValidationResult IsValid(object value, ValidationContext validationContext)
                {
                    if (!string.IsNullOrWhiteSpace(TypeName))
                    {
                        var tempData = Convert.ChangeType(validationContext.ObjectInstance, validationContext.ObjectType);
                        System.Reflection.PropertyInfo propertyInfo = validationContext.ObjectType.GetProperty(TypeName);
                        if (value != null || !string.IsNullOrWhiteSpace(ObjToString(value)))
                        {
                            if (propertyInfo.GetValue(tempData, null) == null)
                            {
                                var error = new ValidationResult(ErrorMsg);
                                return error;
                            }
                        }
                    }
                    else
                    {
                        if (value == null || string.IsNullOrWhiteSpace(ObjToString(value)))
                        {
                            var error = new ValidationResult(ErrorMsg);
                            return error;
                        }
                    }
                   
                    return null;
                }
            }

        }