Flip, get DataAnnotation attributes from friends class

Question

I need to check if a property has a specific attribute defined in its friends class:

[MetadataType(typeof(Metadata))] public sealed partial class Address { private sealed class Metadata { [Required] public string Address1 { get; set; } [Required] public string Zip { get; set; } } } 

How to check which properties defined the Required attribute?

Thanks.

Answer 1

This can be done using a search for nested types:

 public IEnumerable<PropertyInfo> GetRequiredProperties() { var nestedTypes = typeof(Address).GetNestedTypes(BindingFlags.NonPublic); var nestedType = nestedTypes.First(); // It can be done for all types var requiredProperties = nestedType.GetProperties() .Where(property => property.IsDefined(typeof(RequiredAttribute), false)); return requiredProperties; } 

Usage example:

 [Test] public void Example() { var requiredProperties = GetRequiredProperties(); var propertiesNames = requiredProperties.Select(property => property.Name); Assert.That(propertiesNames, Is.EquivalentTo(new[] { "Address1", "Zip" })); } 

Answer 2

Although less elegant Elisha solution, but it works as well :)

Your attribute:

 [AttributeUsage(AttributeTargets.All, AllowMultiple=false)] class RequiredAttribute : System.Attribute { public string Name {get; set; } public RequiredAttribute(string name) { this.Name = name; } public RequiredAttribute() { this.Name = ""; } } 

Some classes:

 class Class1 { [Required] public string Address1 { get; set; } public string Address2 { get; set; } [Required] public string Address3 { get; set; } } 

Using:

 Class1 c = new Class1(); RequiredAttribute ra = new RequiredAttribute(); Type class1Type = c.GetType(); PropertyInfo[] propInfoList = class1Type.GetProperties(); foreach (PropertyInfo p in propInfoList) { object[] a = p.GetCustomAttributes(true); foreach (object o in a) { if (o.GetType().Equals(ra.GetType())) { richTextBox1.AppendText(p.Name + " "); } } } 

Answer 3

Here is my usinjg AssociatedMetadataTypeTypeDescriptionProvider solution:

 var entity = CreateAddress(); var type = entity.GetType(); var metadata = (MetadataTypeAttribute)type.GetCustomAttributes(typeof(MetadataTypeAttribute), true).FirstOrDefault(); var properties = new AssociatedMetadataTypeTypeDescriptionProvider(type, metadata.MetadataClassType).GetTypeDescriptor(type).GetProperties(); bool hasAttribute = HasMetadataPropertyAttribute(properties, "Name", typeof(RequiredAttribute)); private static bool HasMetadataPropertyAttribute(PropertyDescriptorCollection properties, string name, Type attributeType) { var property = properties[name]; if ( property == null ) return false; var hasAttribute = proeprty.Attributes.Cast<object>().Any(a => a.GetType() == attributeType); return hasAttribute; }