Fixes #766, Support in memory filtering after ODataQueryOptions.ApplyTo

[xuzhg]

Fixes #766.

If we have $select and $expand in the request query, the result is collection of ISelectExpandWrapper.

It's not easy for customers to do further. So Add 'Cast' Extension methods on IQueryable and Object.

Basic usage in the controller/action:

IQueryable query = options.ApplyTo(....);
IEnumerable<Customer> results = query.OCast<Customer>(query); // the new extension methods on IQueryable.

foreach (var a in results)
{
    // a is a partial object of Customer if we have $select and $expand.
}

Thanks.

[xuzhg]

@julealgon Please take a look and share your thoughts.

[julealgon]

This looks very convoluted to me. Wouldn't this result in the exact same behavior?

Suggested change

	PropertyInfo propertyInfo = null;
	var properties = type.GetProperties().Where(p => p.Name == propertyName).ToArray();
	if (properties.Length <= 0)
	{
	propertyInfo = null;
	}
	else if (properties.Length == 1)
	{
	propertyInfo = properties[0];
	}
	else
	{
	// resolve 'new' modifier
	propertyInfo = properties.FirstOrDefault(p => p.DeclaringType == type);
	if (propertyInfo == null)
	{
	propertyInfo = properties[0];
	}
	}
	var propertyInfo = type
	.GetProperties()
	.FirstOrDefault(p => p.Name == propertyName && p.DeclaringType == type);

Also, I wonder if it isn't possible to use one of the GetProperty overloads with BindingFlags to get the same behavior in an even cleaner way without having to go through every single property on the type.

Did you check that possibility?

[xuzhg]

I did use BindingFlags, but it seems it can't work. (Maybe what I tried is not enough).

[julealgon]

Can we move each class to its own file?

[julealgon]

Usually, extension classes on interfaces do not have the I in the name:

Suggested change

	public static class IQueryableODataExtension
	public static class QueryableODataExtension

[julealgon]

I think "OCast" is a really bad name that is not intuitive/semantic at all...

I don't have an immediate suggestion, but I'd strongly suggest reconsidering this name.

[julealgon]

If you really want to suppress this, we should add the justification there.

[julealgon]

This is a mistake. as should not be used when the semantic is "the value must be of the type", since it can return null and this will cause a NullReferenceExeception in the foreach.

Suggested change

	IEnumerable collectionPropertyValue = propertyValue as IEnumerable;
	foreach (var item in collectionPropertyValue)
	IEnumerable collectionPropertyValue = (IEnumerable)propertyValue;
	foreach (var item in collectionPropertyValue)

[julealgon]

This looks dangerous to me. We are checking for a match with the interface ISelectExpandWrapper, but then casting to the concrete type.

It could be possible that the value implements the interface but is not the concrete SelectExpandWrapper, which would cause this to fail.

[julealgon]

Duplicated code.

[julealgon]

Looks like this could be extracted to its own separate extension method. To me this is such a generic concern that doesn't need to be inside the OData-specific extension class.

[julealgon]

I'd strongly recommend breaking this into 3 separate tests either manually, or using data-driven tests.

[bogdan-patraucean]

We need this. Any updates??

[mikepizzo]

We had a discussion on this today -- what is the expected behavior if there is a $select applied to the query on which OCast() is called? should we ignore the $select and set all of the properties, or should we only set the properties that are specified in $select and leave it to the developer to somehow understand which properties have been set and which have not?

[bogdan-patraucean]

Awesome! I would expect the select to work. I can't use the select clause with IQueryable so I have to add the needed properties in my endpoint using the Select method.

From my understanding, this PR would fix the issue.

[julealgon]

or should we only set the properties that are specified in $select

Wouldn't that clash with required properties? What if the user didn't select some properties that are marked as required in the original model? If you then try to recreate the same object but only set the selected properties, this will fail.