How to Instantiate ODataQueryOptions

问题

I have a working (simplified) ODataController with the following method.

public class MyTypeController : ODataController
{
  [HttpGet]
  [EnableQuery]
  [ODataRoute("myTypes")]
  public IQueryable<MyType> GetMyTypes(ODataQueryOptions<MyType> options)
  {
    return _repo.myResultsAsQueryable();
  }
}

I would like to be able to call this method from the server and to do this I need to instantiate an ODataQueryOptions which requires an ODataQueryContext.

There are examples of how to do this (Eg. here and here) but they all seem to reference a previous version of OData. The ODataQueryContext constructor currently requires a third argument (ODataPath path) which is not addressed in any examples that I can find.

Edit: @snow_FFFFFF, Here's some more context... I realize that I can simply consume the OData endpoint via a HttpClient but I would like to interact with the IQueryable directly as you say.

The problem is that the application I'm working on allows users to create filters (like a sophisticated search engine) that can be saved and later recalled by other users. From a JS client, they simply lookup the filter by id, and issue a query against the OData endpoint with the filter applied to the query string. This works very well from the client-side but I would like to be able to do something similar from the server-side as well.

This is what I would like to do but how can I instantiate the ODataPath argument?

public IQueryable<MyType> FilterMyTypes(int filterID)
{
  // lookup filter by filterID from db...
  filter = "$filter=Status eq 1"; // for example...

  ODataPath path = // but how can I get the path!!!
  new ODataQueryContext(edmModel, typeof(MyType), path); 

  var uri = new HttpRequestMessage(HttpMethod.Get, "http://localhost:56339/mytypes?" + filter);
  var opts = new ODataQueryOptions<MyType>(ctx, uri);

  var results = new MyTypeController().GetMyTypes(opts);
}

Another application of this would be to support dynamic grouping as below:

[HttpGet]
[Route("myTypes/{filterID:int}/groupby/{groupByFieldName}")]
public IHttpActionResult GroupMyTypes(int filterID, string groupByFieldName)
{
  // For example: get all Active MyTypes and group by AssignedToUserID...

  // Get the results of the filter as IQueryable...
  var results = FilterMyTypes(filterID);

  // group on groupByFieldName
  var grouped = results.GroupBy(x => GetPropertyValue(x,groupByFieldName));

  // select the groupByFieldName and the count
  var transformedResults = grouped.Select(g => new { g.Key, Count = g.Count() });

  return Ok(transformedResults);
}

回答1:

Sure. ODataPath is a list of ODataPathSegment(s) which should follow up the OData Uri spec.

In Web API OData, it's easy to instantiate an ODataPath, for example:

IEdmModel model = GetEdmModel(); 
IEdmEntitySet entitySet = model.EntityContainer.FindEntitySet(setName); 
ODataPath path = new ODataPath(new EntitySetPathSegment(entitySet));

The above path follows up the OData spec that it has the odata template as:

~/entityset

More test cases (codes) can be found here

回答2:

Your odata controller is providing an HTTP interface to your data, shouldn't you access it via HTTP (even if from the server)? There is a VS add-in to generate odata client code here:

https://visualstudiogallery.msdn.microsoft.com/9b786c0e-79d1-4a50-89a5-125e57475937

Or, if you are doing this from within the same project, why not a common method that returns the IQueryable that could be called from your code or from the controller?

UPDATE: Based on more information in the original question:

If you have ODataQueryOptions defined in a controller method, it will allow you to parse the well-formed odata query that is calling that method. I have used this when I needed to translate parts of an odata query because I needed to query multiple data sources to return the final result.

It sounds like you want something that takes non-odata parameters and options. For this, you probably need to look at custom Actions and or Functions (if you are just returning data, probably a function):

http://www.asp.net/web-api/overview/odata-support-in-aspnet-web-api/odata-v4/odata-actions-and-functions

UPDATE #2: And after more detailed reading, I think I missed your point - I don't have the answer, but I'll play around with it. Can't you just reform the URL itself (as opposed to instantiating the query options?

UPDATE #3: I think you are going to have a hard time tricking it into thinking it is getting an odata request...that isn't really an odata request. Back to the second option mentioned in my original answer - why not a common method that you can use and the odata controller can use - something like this:

// some sort of helper class
public class HelperObject
{
    public static IQueryable<MyType> GetGroupedValues(int filterID, string groupByFieldName)
    {
        // all your code/logic here
    }
}

// your odata controller uses the helper
[HttpGet]
[Route("myTypes/{filterID:int}/groupby/{groupByFieldName}")]
public IHttpActionResult GroupMyTypes(int filterID, string groupByFieldName)
{
    return Ok(HelperObject.GetGroupedValues(filterID, groupByFieldName));
}

// ... and so does your other code that wants to do the same thing
var x = HelperObject.GetGroupedValues(filterID, groupByFieldName);

来源：https://stackoverflow.com/questions/33572659/how-to-instantiate-odataqueryoptions

标签

.net

odata

asp.net-web-api2