.net - C# Buddy Classes / Meta Data and Reflection

Question

I am trying to use reflection to check if properties on a given class have a ReadOnly attribute set. The classes I am using are MVC View Models (using a partial "buddy" class for the metadata.

 public partial class AccountViewModel  
{
    public virtual Int32 ID { get; set; } 
    public virtual decimal Balance { get; set; }    

} 
[MetadataType(typeof(AccountViewModelMetaData))]
public partial class AccountViewModel  
{
    class AccountViewModelMetaData
    {
        [DisplayName("ID")]
        public virtual Int32 ID { get; set; }

        [DisplayName("Balance")]
        [DataType(DataType.Currency)] 
        [ReadOnly(true)]
        public virtual decimal Balance { get; set; }

    }
}

I want to check if "Balance" has the ReadOnly property. If i set the ReadOnly attribute on the Balance property of AccountViewModel, i can retrieve it this way:

Type t = typeof(AccountViewModel);
PropertyInfo pi = t.GetProperty("Balance");  
bool isReadOnly =  ReadOnlyAttribute.IsDefined(pi,typeof( ReadOnlyAttribute);

I can't retrieve the attribute info if it is on the meta data class. How can i check if the attribute exists? I have meta data classes defined for all my view models, and need a generic way to check for attributes on meta data classes.

Any suggestions?

Answer 1

the solution is to use GetCustomAttributes to get MetaData types and check the properties on those as well...

Type t = typeof(MyClass);
PropertyInfo pi = t.GetProperty(PropertyName);  
bool isReadOnly = ReadOnlyAttribute.IsDefined(pi, typeof(ReadOnlyAttribute));

if (!isReadOnly)
{
    //check for meta data class.
    MetadataTypeAttribute[] metaAttr = (MetadataTypeAttribute[])t.GetCustomAttributes(typeof(MetadataTypeAttribute),true);

    if (metaAttr.Length > 0)
    {
        foreach (MetadataTypeAttribute attr in metaAttr)
        {
            t = attr.MetadataClassType;
            pi = t.GetProperty(PropertyName);

            if (pi != null) isReadOnly = ReadOnlyAttribute.IsDefined(pi, typeof(ReadOnlyAttribute));

            if (isReadOnly) break;
        }
    }
}