Enumerate ICollection<T> property of class using Reflection
I'm trying to create a base class for my POCO objects in .NET 4, which will have an Include(string path) method, where path is a "." delimited navigation path of nested ICollection properties of the inheriting class to be enumerated.
For example, given the following classes;
public class Region
{
public string Name { get; set; }
public ICollection<Country> Countries { get; set; }
}
public partial class Region : EntityBase<Region> {}
public class Country
{
public string Name { get; set; }
public ICollection<City> Cities { get; set; }
}
public partial class Country : EntityBase<Country> {}
public class City
{
public string Name { get; set; }
}
public partial class City : EntityBase<City> {}
I want to be able to do something like this;
Region region = DAL.GetRegion(4);
region.Include("Countries.Cities");
So far I have the following;
public class EntityBase<T> where T : class
{
public void Include(string path)
{
// various validation has been omitted for brevity
string[] paths = path.Split('.');
int pathLength = paths.Length;
PropertyInfo propertyInfo = type(T).GetProperty(paths[0]);
object propertyValue = propertyInfo.GetValue(this, null);
if (propertyValue != null)
{
Type interfaceType = propertyInfo.PropertyType;
Type entityType = interfaceType.GetGenericArguments()[0];
// I want to do something like....
var propertyCollection = (ICollection<entityType>)propertyValue;
foreach(object item in propertyCollection)
{
if (pathLength > 1)
{
// call Include method of item for nested path
}
}
}
}
}
Clearly, the "var l开发者_开发技巧ist = ...>" line doesn't work but you hopefully get the gist, and the foreach will not work unless is the propertyCollection is enumerable.
So it's the last bit, i.e. how do I enumerate an ICollection property of a class when I do not know the type of T until runtime?
Thanks
You don’t need Reflection for this. In order to enumerate it, you only need an IEnumerable
. ICollection<T>
inherits IEnumerable
, so all of your collections will be enumerables. Therefore,
var propertyCollection = (IEnumerable) propertyValue;
foreach (object item in propertyCollection)
// ...
will work.
Generics are normally used when the client can resolve the generic type at compile-time.
Leaving that aside, since all you need to do is enumerate the propertyCollection
(viewing each element of the sequence simply as a System.Object
) all you need to do is:
var propertyCollection = (IEnumerable)propertyValue;
foreach(object item in propertyCollection)
{
...
}
This is perfectly safe since ICollection<T>
extends IEnumerable<T>
, which in turn extends IEnumerable
. What T
actually ends up being at run-time is irrelevant since the loop only requires object
.
The real question is: Is System.Object
sufficient for your purposes inside the loop?
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