How to get a list of properties with a given attribute

Question

I have a type  t  and I would like to get a list of the public properties that have the attribute MyAttribute  The attribute is marked with AllowMultiple   false  like this    AttributeUsage AttributeTargets Property  AllowMultiple   false     Currently what I have is this  but I m thinking there is a better way   foreach  PropertyInfo prop in t GetProperties          object   attributes   prop GetCustomAttributes typeof MyAttribute   true       if  attributes Length    1                   Property with my custom attribute           How can I improve this  My apologies if this is a duplicate  there are a ton of reflection threads out there   seems like it s quite a hot topic

User · Answer

As far as I know  there isn t any better way in terms of working with Reflection library in a smarter way  However  you could use LINQ to make the code a bit nicer   var props   from p in t GetProperties               let attrs   p GetCustomAttributes typeof MyAttribute   true              where attrs Length    0 select p      Do something with the properties in  props    I believe this helps you to structure the code in a more readable fashion

User · Answer

If you deal regularly with Attributes in Reflection  it is very  very practical to define some extension methods  You will see that in many projects out there  This one here is one I often have   public static bool HasAttribute lt T gt  this ICustomAttributeProvider provider  where T   Attribute     var atts   provider GetCustomAttributes typeof T   true     return atts Length  gt  0      which you can use like typeof Foo  HasAttribute lt BarAttribute gt      Other projects  e g  StructureMap  have full-fledged ReflectionHelper classes that use Expression trees to have a fine syntax to identity e g  PropertyInfos  Usage then looks like that   ReflectionHelper GetProperty lt Foo gt  x   gt  x MyProperty  HasAttribute lt BarAttribute gt

User · Answer

There s always LINQ   t GetProperties   Where      p  gt p GetCustomAttributes typeof MyAttribute   true  Length    0

User · Answer

In addition to previous answers  it s better to use method Any   instead of check length of the collection   propertiesWithMyAttribute   type GetProperties      Where x   gt  x GetCustomAttributes typeof MyAttribute   true  Any       The example at dotnetfiddle  https   dotnetfiddle net 96mKep

User · Answer

The solution I end up using most is based off of Tomas Petricek s answer  I usually want to do something with both the attribute and property   var props   from p in this GetType   GetProperties               let attr   p GetCustomAttributes typeof MyAttribute   true              where attr Length    1             select new   Property   p  Attribute   attr First   as MyAttribute

User · Answer

var props   t GetProperties   Where                  prop   gt  Attribute IsDefined prop  typeof MyAttribute       This avoids having to materialize any attribute instances  i e  it is cheaper than GetCustomAttribute s

[c#] How to get a list of properties with a given attribute?

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