When to use IQueryable as Return type in web service

debugcn 投稿 Dev

Pavan Gawade

If defined return type as IQueryable then my ajax call fail some time.

        [HttpGet]
    public IQueryable<Banner> GetBannerForExcel()
    {
        return this._banneruow.Repository.GetAll();
    }

I am getting 500 Internal Server Error and unable to debug also;

XML Parsing Error: no element found Location: moz-nullprincipal:{4acaf0ef-4230-404d-ae26-304916e1c044} Line Number 1, Column 1:

So when I use return type List<Banner> it works perfect without error.

Vlad Bezden

If your controller returns OData format, the response body from your action that returns IQueryable will contain more information such as next page of data, odata metadata. IQueryable supports further filtering, paging, but it doesn't support random access via indexer. List supports random access via indexer and doesn't support further filtering. In your case if you need only data on the client side then return List or IEnumerable.

IQueryable is better choice for data-tier (server side), because it defer execution.

I also would recommend you to trace what you are getting back from a server when you use IQueryable and List using browser dev tools, or Fiddler

You can find more information here:

IQueryable, IEnumerable or List

Implement Efficient Data Paging

To return IQueryable or not return IQueryable

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編集2021-07-5

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