How to transform a fixed length string file structure to any object

FixedLengthStringToObject.cs

    public class LineDefinitionAttribute : Attribute
    {
        public LineDefinitionAttribute(int size, int startIndex, string format = "")
        {
            Size = size;
            StartIndex = startIndex;
        }

        public int Size { get; set; }
        public int StartIndex { get; set; }
        public string Format { get; set; }
    }
    
    public class Item
    {
        [LineDefinition(size: 1, startIndex: 0)]
        public int Id { get; set; }
        
        [LineDefinition(size: 50, startIndex: 1)]
        public string Name { get; set; }        
    }
    
        public static class StringExtensions
    {
        public static T ToObject<T>(this string fixedLengthString) where T : new()
        {
            var properties = typeof(T).GetProperties().Where(p => p.GetCustomAttributes(typeof(LineDefinitionAttribute), false).Count() > 0);

            if (!properties.Any())
                return default;

            var obj = Activator.CreateInstance<T>();

            foreach (var property in properties)
            {
                var attribute = property.GetCustomAttributes(false).FirstOrDefault(p => p.GetType() == typeof(LineDefinitionAttribute));

                if (attribute == null)
                    continue;

                var lineDefinitionAttribute = (LineDefinitionAttribute)attribute;

                var stringValue = fixedLengthString.Substring(lineDefinitionAttribute.StartIndex, lineDefinitionAttribute.Size);

                if (property.PropertyType == typeof(int))
                    property.SetValue(obj, int.Parse(stringValue));
                else if (property.PropertyType == typeof(long))
                    property.SetValue(obj, long.Parse(stringValue));
                else if (property.PropertyType == typeof(decimal))
                    property.SetValue(obj, decimal.Parse(stringValue));
                else if (property.PropertyType == typeof(DateTime))
                    property.SetValue(obj, DateTime.ParseExact(stringValue, lineDefinitionAttribute.Format, CultureInfo.InvariantCulture));
                else
                    property.SetValue(obj, stringValue);

            }

            return obj;

        }
    }