Question

I’d like to implement dynamic WebGrid Creation from Model.

The Idea is to Create a Grid from Model “Description” by annotating the Model Properties with attributes.

class Model
{
   public List<Product> Products {get;set;}

}

class Product 
{
   [GridColumn]
   public String Name {get;set;}
   ....

}

Then I’d like to Get By Reflection All properties marked by this Attribute.

public WebGridColumns[] ColumnsFromModel(object model)
{
   // Here model is List<T> so how get all custom attributes of List<T> ?


}

Answer 1

You can create a simple extension method that will get the attributes you want from an implementation of the ICustomAttributeProvider interface (which is implemented by any representation of a .NET construct that can have an attribute on it):

public static IEnumerable<T> GetCustomAttributes(
    this ICustomAttributeProvider provider, bool inherit) where T : Attribute
{
    // Validate parameters.
    if (provider == null) throw new ArgumentNullException("provider");

    // Get custom attributes.
    return provider.GetCustomAttributes(typeof(T), inherit).
        Cast<T>();
}

From there, it’s a call over all the PropertyInfo instances on a type, like so:

var attributes = 
    // Get all public properties, you might want to
    // call a more specific overload based on your needs.
    from p in obj.GetType().GetProperties()

    // Get the attribute.
    let attribute = p.GetCustomAttributes<GridColumnAttribute>().
        // Assuming allow multiple is false.
        SingleOrDefault().

    // Filter out null properties.
    where attribute != null

    // Map property with attribute.
    select new { Property = p, Attribute = attribute };

From there, you can call the GetType method on any object instance and run it through the above query to get the PropertyInfo instance and the attribute that is applied to it.