C# Language Reflection Custom Attributes
Example
Find properties with a custom attribute - MyAttribute
var props = t.GetProperties(BindingFlags.NonPublic | BindingFlags.Public |
BindingFlags.Instance).Where(
prop => Attribute.IsDefined(prop, typeof(MyAttribute)));
Find all custom attributes on a given property
var attributes = typeof(t).GetProperty("Name").GetCustomAttributes(false);
Enumerate all classes with custom attribute - MyAttribute
static IEnumerable<Type> GetTypesWithAttribute(Assembly assembly) {
foreach(Type type in assembly.GetTypes()) {
if (type.GetCustomAttributes(typeof(MyAttribute), true).Length > 0) {
yield return type;
}
}
}
Read value of a custom attribute at runtime
public static class AttributeExtensions
{
/// <summary>
/// Returns the value of a member attribute for any member in a class.
/// (a member is a Field, Property, Method, etc...)
/// <remarks>
/// If there is more than one member of the same name in the class, it will return the first one (this applies to overloaded methods)
/// </remarks>
/// <example>
/// Read System.ComponentModel Description Attribute from method 'MyMethodName' in class 'MyClass':
/// var Attribute = typeof(MyClass).GetAttribute("MyMethodName", (DescriptionAttribute d) => d.Description);
/// </example>
/// <param name="type">The class that contains the member as a type</param>
/// <param name="MemberName">Name of the member in the class</param>
/// <param name="valueSelector">Attribute type and property to get (will return first instance if there are multiple attributes of the same type)</param>
/// <param name="inherit">true to search this member's inheritance chain to find the attributes; otherwise, false. This parameter is ignored for properties and events</param>
/// </summary>
public static TValue GetAttribute<TAttribute, TValue>(this Type type, string MemberName, Func<TAttribute, TValue> valueSelector, bool inherit = false) where TAttribute : Attribute
{
var att = type.GetMember(MemberName).FirstOrDefault().GetCustomAttributes(typeof(TAttribute), inherit).FirstOrDefault() as TAttribute;
if (att != null)
{
return valueSelector(att);
}
return default(TValue);
}
}
Usage
//Read System.ComponentModel Description Attribute from method 'MyMethodName' in class 'MyClass'
var Attribute = typeof(MyClass).GetAttribute("MyMethodName", (DescriptionAttribute d) => d.Description);
