Web API OData Typeless support for $select query option - asp.net-web-api-odata

Question

I am working with the new typeless support in ASP.NET Web API 2 OData. I am interested in providing support for the $select query option. How do I omit the structural properties from the EdmEntityObject that were not selected by the $select query option?
The following is a sample of the Web API Configuration for a very simple example working with a typeless model.
public static IEdmModel BuildEdmModel()
{
var model = new EdmModel();
var container = new EdmEntityContainer("Model", "OData");
var product = new EdmEntityType("Model", "Product");
var productKey = product.AddStructuralProperty("ID", EdmPrimitiveTypeKind.Guid);
product.AddKeys(productKey);
product.AddStructuralProperty("Name", EdmPrimitiveTypeKind.String);
product.AddStructuralProperty("Price", EdmPrimitiveTypeKind.Double);
model.AddElement(product);
model.AddElement(container);
model.SetIsDefaultEntityContainer(container, true);
container.AddEntitySet("Products", product);
return model;
}
public static void Register(HttpConfiguration config)
{
config.Routes.MapODataRoute("ODataRoute", "odata", BuildEdmModel());
}
The following is a partial snippet from a simple ODataController
public EdmEntityObjectCollection Get()
{
var path = Request.GetODataPath();
var edmType = path.EdmType;
var collectionType = edmType as IEdmCollectionType;
var entityType = collectionType.ElementType.AsEntity();
var entitySetName = entityType.EntityDefinition().Name;
var model = Request.GetEdmModel();
var queryContext = new ODataQueryContext(Request.GetEdmModel(), entityType.Definition);
var queryOptions = new ODataQueryOptions(queryContext, Request);
return GetData(Request.GetEdmModel(), queryOptions);
}
public static EdmEntityObjectCollection GetData(IEdmModel edmModel, ODataQueryOptions queryOptions)
{
var selectedPropertyNames = new string[0];
// determine the selected property names
if (queryOptions.SelectExpand != null && queryOptions.SelectExpand.SelectExpandClause != null && (!queryOptions.SelectExpand.SelectExpandClause.AllSelected || queryOptions.SelectExpand.SelectExpandClause.SelectedItems.OfType<WildcardSelectItem>().Any()))
{
selectedPropertyNames = queryOptions.SelectExpand.RawSelect.Split(',');
}
// TODO: Now that we have the selected properties, how do I remove the structural properties from the EdmEntityObject that were not selected by the $select query option?
var productSchemaType = edmModel.FindDeclaredType(string.Format("{0}.Product", "Model"));
var productEntityType = productSchemaType as IEdmEntityType;
var productEntityTypeReference = new EdmEntityTypeReference(productEntityType, true);
var products = new EdmEntityObjectCollection(new EdmCollectionTypeReference(new EdmCollectionType(productEntityTypeReference), true));
var productWindows = new EdmEntityObject(productEntityTypeReference);
productWindows.TrySetPropertyValue("ID", new Guid("52D811A0-9065-4B83-A2E8-0248FBA9FBF5"));
productWindows.TrySetPropertyValue("Name", "Microsoft Windows 8");
productWindows.TrySetPropertyValue("Price", 179.99);
var productOffice = new EdmEntityObject(productEntityTypeReference);
productOffice.TrySetPropertyValue("ID", new Guid("CB39EBD0-4751-4D5F-A76C-78FCC7A9CE1A"));
productOffice.TrySetPropertyValue("Name", "Microsoft Office 2013");
productOffice.TrySetPropertyValue("Price", 399.99);
products.Add(productWindows);
products.Add(productOffice);
return products;
}
This will output:
{
"odata.metadata":"http://localhost:59511/odata/$metadata#Products","value":[
{
"ID":"52d811a0-9065-4b83-a2e8-0248fba9fbf5","Name":"Microsoft Windows 8","Price":179.99
},{
"ID":"cb39ebd0-4751-4d5f-a76c-78fcc7a9ce1a","Name":"Microsoft Office 2013","Price":399.99
}
]
}
If the user applies a $select query option, for example /odata/Products?$select=Name. This should result in the following output:
{
"odata.metadata":"http://localhost:59511/odata/$metadata#Products","value":[
{
"Name":"Microsoft Windows 8"
},{
"Name":"Microsoft Office 2013"
}
]
}
Any help would be greatly appreciated

Answer 1

The following works for me.
var oDataProperties = Request.ODataProperties()
oDataProperties.SelectExpandClause = queryOptions.SelectExpand.SelectExpandClause;
The extension function is in System.web.OData.dll v5.2.0.0.

Answer 2

Here's my code.
private void ApplySelectExpand(SelectExpandQueryOption selectExpand)
{
if (selectExpand != null)
{
Request.SetSelectExpandClause(selectExpand.SelectExpandClause);
}
}

Answer 3

There are two ways to solve your problem if I understood your question correctly.
Call the ApplyTo method of ODataQueryOptions on the IQueryable result
return queryOptions.ApplyTo(products);
Add attribute Queryable on the GetData method and let WebAPI handles the query option
[Queryable]
public static EdmEntityObjectCollection GetData(IEdmModel edmModel)
{...}