error requesting $count

[mansurdegirmenci]

   [HttpGet]
   public async Task<IActionResult> Get(ODataQueryOptions<PhotoDto> options)
   {
       var result = await _dataListContext.Photos.GetQueryAsync(_mapper, options);
       return Ok(result);
   }

url: https://localhost:5001/api/Photos/$count

When I make a request to the specified url, it gives the following error, other requests work fine. The version I use is the latest version.

Microsoft.OData.ODataException: The value of type 'Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1[[WebUI.DataTransferObject.Server.PhotoDto, WebUI, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' could not be converted to a raw string.

[BlaiseD]

May not be supported. Best to add a test so we can see it fail. See examples of supported usage here and here.

[HHDanim]

Digging through the sources I found that GetQuery() / GetQueryAsync() sets the OData feature "TotalCount" if you request $count. So this is my solution/workaround I came up with to get $count working:

    public IActionResult Get([FromServices] ODataQueryOptions<Entity> options) {
        IQueryable<Entity> query = dbContext.Entities.GetQuery(mapper, options);
        return options.Count?.Value == true ? Ok(options.Request.ODataFeature().TotalCount) : Ok(query);
    }

[hurcane]

It's almost a year later, but I think there is a better workaround than the one posted by @HHDanim. The problem with the original workaround is that it is causing an incorrect result when the count is supposed to be included with results.

The query https://mysite.com/odata/Entity/$count correctly returns just the count.

But the query https://mysite.com/odata/Entity/$count=true is returning the following:

{
    "@odata.context": "https://mysite.com/odata/$metadata#Edm.Int64",
    "value": 96
}

The correct response should be of the form:

{
    "@odata.context": "https://mysite.com/odata/$metadata#Edm.Int64",
    "@odata.count": 96,
    "value": [
        {
            "Property1":"true",
            "AnotherProperty":"some value"
        },
        {
            "Property1":"true",
            "AnotherProperty":"another value"
        }
...
    ]
}

A better workaround is the following:

public IActionResult Get([FromServices] ODataQueryOptions<Entity> options) 
{
    IQueryable<Entity> query = dbContext.Entities.GetQuery(mapper, options);
    return options.Context.Path.LastSegment is Microsoft.OData.UriParser.CountSegment ?
        Ok(options.Request.ODataFeature().TotalCount) : Ok(query);
}