Azure 移动应用服务器在 GET 上不返回 DBGeography

Question

My instance of Microsoft Azure Mobile App Server will happily store a DBGeography POINT() as a table column, which is contained in the JSON data confirming that a POST has been made.

My 'Location' data object:

public DbGeography Location { get; set; }

    [NotMapped]
    public double Longitude { get; set; }
    [NotMapped]
    public double Latitude { get; set; }

My controller:

public async Task<IHttpActionResult> PostI4Item([FromBody] IslandFourEntity item)
    {
        var coordinates = DbGeography.FromText($"POINT({item.Longitude} {item.Latitude})");
        item.Location = coordinates;
        
        IslandFourEntity current = await InsertAsync(item);
        return CreatedAtRoute("Tables", new { id = current.Id }, current);
    }

Postman response after 'POST' request:

{
"body": "Test body value",
"subject": "Test subject value",
"type": "type",
"location": {
    "geography": {
        "coordinateSystemId": 4326,
        "wellKnownText": "POINT (172.590401 -43.539994)"
    }
},
"longitude": 172.590401,
"latitude": -43.539994,
"id": "58542f5ee84d4867ae1f3d2c3b098b1b",
"version": "AAAAAAAAD6I=",
"createdAt": "2021-03-05T00:16:12.292Z",
"updatedAt": "2021-03-05T00:16:12.731Z",
"deleted": false

}

However if you GET all table values, or just one individual item, the column containing the DBGeography item isn't contained within (despite definitely being saved in the database.)

Default GET response for that record:

{
"deleted": false,
"updatedAt": "2021-03-05T00:16:12.731Z",
"createdAt": "2021-03-05T00:16:12.292Z",
"version": "AAAAAAAAD6I=",
"id": "58542f5ee84d4867ae1f3d2c3b098b1b",
"type": "type",
"subject": "Test subject value",
"body": "Test body value"

}

As you can see, every other column was returned except for 'Location'.

So this question is probably more for anyone who has had experience with Microsoft Azure Mobile App Services, but how can you modify the default Query() method to serialise DBGeography into a string?

Answer 1

Ultimately, you get an IQueryable<T> back and then it is serialized by the ASP.NET OData (v3) system or the Node.js system (you don't say which you are using). There are two issues here - what the IQueryable is returning, and what oData does with it.

Since it is an OData v3 endpoint, try adding ?$expand=location to see if that will expand the output. Read up on the $expand option in the docs - section 5.1.3 covers $expand.