ODataQuery

This package enables server-side filtering, sorting and pagination of any IQueryable<T> using OData syntax and without needing an EDM model. This is achieved simply by adding [ODataQueryable] to any such API.

How to use

Add a reference to Nuget package ODataQuery.

// Import this namespace
using ODataQuery;

[Route("api/version")]
public class VersionController
{
  // Add attribute ODataQueryable
  [HttpGet, ODataQueryable]
  public IQueryable<Version> Get()
  {
    // Source data can be anything (most likely an EF query)...
    var versions = new[] {
      new Version(1, 0),
      new Version(1, 1),
      new Version(2, 0),
      new Version(3, 0),
    };
    // ... as long as it's IQueryable<T>
    return versions.AsQueryable();
  }
}

Now you can filter, sort and paginate versions:

GET /api/version?$filter=major gt 2&$orderby=major desc

would return this response:

{
  "value": [
    { "major": 3, "minor": 0 },
    { "major": 2, "minor": 0 }
  ]
}

ODataQueryable changes the shape of your response to a standard OData response:

• { "value": [...] } by default;
• { "@odata.count": 42, "value": [...] } if you used the $count option.

Limitations

The goal of this project is to enable easy server-side processing of datagrids, lists and co. in web applications, while being secure by default (e.g. you can't fetch the full DB through $expand, because it's not supported).

Currently it has the following limitations:

• There is no routing, only query string processing.
• Not all system options are supported, only: $filter, $search, $orderby, $skip, $top, $select and $count.
• Only a subset of the full OData 4.0.1 is supported, see below for detailed support.
• Error reporting is bad.

That last point warrants an explanation. You will get a ParseException if the query string is not correctly formatted and the message will indicate where it failed, but the error message can often be unhelpful: e.g. mentioning a single expected character instead of a full token.

You will also get various exceptions if the query can be parsed but is semantically incorrect (properties that don't exist, type errors, invalid date literals).

In all cases this will likely result in a 500 Internal Error, although a 400 code (bad request) would be more appropriate.

With respect to error-friendliness, this API is not meant to be used to build public, open APIs.

Usage

ODataQueryable attribute

Apply [ODataQueryable] to automatically apply OData query string to an IQueryable<T> result and return an OData response.

If the method throws, doesn't return a success code (2xx) or doesn't return an IQueryable<T> result then this attribute does nothing.

Manual application

This package adds an extension method to IQueryable<T> to apply the query string manually in your code:

IQueryable<T> source;
// Does not apply $count
IQueryable<T> result = source.OData(HttpContext.Request.Query);
// Applies $count and return result in out parameter
int count;
IQueryable<T> result = source.OData(HttpContext.Request.Query, out count);

Fine-grained

Two extension methods let you apply $filter or $orderby directly from a string:

IQueryable<T> source;
IQueryable<T> result = source.ODataFilter("amount gt 1000")
                             .ODataOrderBy("release desc,id");

Extensions to OData 4.0.1

This library follows OData conventions, with the following extensions:

• DateTime is supported (OData only supports DateTimeOffset). Literals without a timezone parse as DateTime, literals with a timezone as DateTimeOffset.

• in operator can have an empty list on right hand side: x in (). This is forbidden by OData grammar but it is accepted by this library and evaluates to false.

Supported grammar

This library implements a subset of OData 4.0.1.

Only $filter, $orderby, $top, $skip and $count are supported.

Types and Literals

Supported: Numeric types, DateOnly, DateTime, DateTimeOffset, bool, string, enums.

Literals:

• strings delimited with single quotes, double single-quote escape: 'Marc''s house'
• numbers, exponents are not supported: -? [0-9]+ (. [0-9]+)?
• dates, day then optional time then optional timezone (Z or +-0000), e.g. 2019-07-22, 2019-07-22T14:15:00, and 2019-07-22T14:15:00+0200
• enums, either as string or ints. Old syntax prefixed by type name is not supported: 'red'.
• true, false
• null

Identifiers

Starting with a letter or _, then followed by letters, digits and _.

Identifier are looked for in a case-insensitive way in model. So id eq 3 will match a property Id on the server.

Path to subproperties such as Address/City are not supported.

Operators

Comparison operators:

• Supported: eq, ne, lt, le, gt, ge, in
• Not supported: has

Logical operators:

• Supported: and, or, not

Arithmetic operators:

• Not supported: add, sub, mul, div, divby, mod.

Grouping operators:

• Supported: ()

Functions

String functions:

• Supported: contains, endswith, startswith, length, indexof, substring, tolower, toupper, trim, concat

Date functions:

• Supported: year, month, day, hour, minute, second, date.
• Not supported: fractionalseconds, time, totaloffsetminutes, now, mindatetime, maxdatetime.

Math functions:

• Supported: round, floor, ceiling.

Type functions:

• Not supported: cast, isof.

Geo function:

• Not supported: geo.distance, geo.length, geo.intersects.

Custom functions are supported. They must be registered globally with ODataQueryableOptions.RegisterFunction() before using them. Registration takes three parameters:

• string name: the name of the function as it appears in the query string. Following OData convention, it must include a namespace, e.g. my.function.
• Func<Expression[], Expression> mapper: a delegate that builds the resulting Expression from its arguments.
• params Type[] argTypes: an optional list of input argument types. When used, ODataQueryable will automatically add Convert expression nodes where required. This is useful as conversion are commonly required, e.g. different exact number types, or nullable structs.

$filter

Filter must evaluate to any boolean expression and is applied as Where.

Collection predicates such as any and all are not supported, neither are paths to sub-properties such as Address/City.

$search

The semantics of what search does is up to the application: which fields? case-sensitive? starts, contains or exact match?

For this reason, the attribute ODataQueryable simply binds a $search query string to a search parameter (if any), so that you can apply the search yourself.

$orderby

Sorting is a comma-separated list of expressions, optionnally followed by keywords asc and desc.

It is applied as OrderBy, ThenBy, respectively OrderByDescending, ThenByDescending.

Note: OData grammar doesn't allow spaces before or after commas in $orderby, neither does this library. So $orderby=name, id will throw.

$select

Projecting only supports a list of plain identifiers.

It is applied as a Select that returns a lightweight IDictionary<string, object> that is meant to be serialized (it is not fully functional and most methods throw NotImplementedException).

$count

If $count=true is in the query string, the response will have an additional @odata.count property set to the count of results just after applying filter, i.e. before applying $top, $skip, and $orderby.

It is applied as a call to Count (so 2 queries are executed).

Note: only the OData 4.0 $count option is supported. Previously it was $inline-count=allpages, which is not supported by this library.

$top and $skip

Both supported as plain integers, applied as Take and Skip calls.

Note: before v1.1 this package looked for $take instead of $top which is not the OData standard. For backward compatibility, $take is still accepted as a synonym of $top but it's usage is discouraged.