Question

Similar: How I can find Data Annotation attributes and their parameters using reflection

However, when attempting to gather the custom attribute, I always get back the same result. An empty ScriptIgnore.

PropertyInfo[] Properties = Entity.GetType().GetProperties();
foreach (PropertyInfo Property in Properties)

Upon debug, this line of code

var annotes = Property.GetCustomAttributes(typeof(ScriptIgnoreAttribute), false);

(I also tried using true)

looks like this

annotes | {System.Web.Script.Serialization.ScriptIgnoreAttribute[0]}

However, Property is defined as a class property like this

public virtual Lot Lot { get; set; }

There is no [ScriptIgnore] attribute attached. Moreover, when I have tried this on Property when it was defined like this

[ScriptIgnore]
public virtual ICollection<Lot> Lots { get; set; }

I get back the same result as above

annotes | {System.Web.Script.Serialization.ScriptIgnoreAttribute[0]}

How can I use reflection to determine if an attribute exists? Or other means if possible, I also tried

var attri = Property.Attributes;

but it did not contain any attributes.

Answer 1

The following code works:

using System.Web.Script.Serialization;
public class TestAttribute
{
  [ScriptIgnore]
  public string SomeProperty1 { get; set; }

  public string SomeProperty2 { get; set; }

  public string SomeProperty3 { get; set; }

  [ScriptIgnore]
  public string SomeProperty4 { get; set; }
}

Define a static extension:

public static class AttributeExtension
{
  public static bool HasAttribute(this PropertyInfo target, Type attribType)
  {
    var attribs = target.GetCustomAttributes(attribType, false);
    return attribs.Length > 0;
  }
}

Put the following sample code into a method and it picks up the attribute correctly – including ICollection by the way:

  var test = new TestAttribute();
  var props = (typeof (TestAttribute)).GetProperties();
  foreach (var p in props)
  {
    if (p.HasAttribute(typeof(ScriptIgnoreAttribute)))
    {
      Console.WriteLine("{0} : {1}", p.Name, attribs[0].ToString());
    }
  }

  Console.ReadLine();

NOTE: if you’re using EF dynamic proxy classes, I think you will need to use ObjectContext.GetObjectType() to resolve to the original class before you can get the attributes, since the EF-generated proxy class will not inherit the attributes.