From https://msdn.microsoft.com/en-us/library/71s1zwct(v=vs.110).aspx

Retrieve_Custom_Attributes.cs

public static void GetAttribute(Type t)
{
    DeveloperAttribute att;

    // Get the class-level attributes.

    // Put the instance of the attribute on the class level in the att object.
    att = (DeveloperAttribute) Attribute.GetCustomAttribute (t, typeof (DeveloperAttribute));

    if (att == null)
    {
        Console.WriteLine("No attribute in class {0}.\n", t.ToString());
    }
    else
    {
        Console.WriteLine("The Name Attribute on the class level is: {0}.", att.Name);
        Console.WriteLine("The Level Attribute on the class level is: {0}.", att.Level);
        Console.WriteLine("The Reviewed Attribute on the class level is: {0}.\n", att.Reviewed);
    }

    // Get the method-level attributes.

    // Get all methods in this class, and put them
    // in an array of System.Reflection.MemberInfo objects.
    MemberInfo[] MyMemberInfo = t.GetMethods();

    // Loop through all methods in this class that are in the
    // MyMemberInfo array.
    for (int i = 0; i < MyMemberInfo.Length; i++)
    {
        att = (DeveloperAttribute) Attribute.GetCustomAttribute(MyMemberInfo[i], typeof (DeveloperAttribute));
        if (att == null)
        {
            Console.WriteLine("No attribute in member function {0}.\n" , MyMemberInfo[i].ToString());
        }
        else
        {
            Console.WriteLine("The Name Attribute for the {0} member is: {1}.",
                MyMemberInfo[i].ToString(), att.Name);
            Console.WriteLine("The Level Attribute for the {0} member is: {1}.",
                MyMemberInfo[i].ToString(), att.Level);
            Console.WriteLine("The Reviewed Attribute for the {0} member is: {1}.\n",
                MyMemberInfo[i].ToString(), att.Reviewed);
        }
    }
}