Custom Attributes in C#?

Short answer: Real Use Cases Validation frameworks Logging metadata Role-based security API documentation metadata Custom Attribute Example [AttributeUsage(AttributeTargets.Property)] public class RequiredAttribute : Attribute {} Usage Example public class Employee

Example code

{ [Required] public string Name { get; set; }
} Validation Logic public static void Validate(object obj)
{
var properties = obj.GetType().GetProperties();
foreach (var prop in properties)
{
var isRequired = prop.GetCustomAttributes(typeof(RequiredAttribute), false).Any();
if (isRequired && prop.GetValue(obj) == null) throw new Exception($"{prop.Name} is required"); }
}

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.