Query options

Article
01/29/2021

Applies To: # OData client v7 supported OData Client V7

There are mainly 2 ways to add Query Options to a DataServiceQuery

Using AddQueryOption method.
Using strongly typed C# LINQ query methods.

AddQueryOption Method

The following example shows how to use to the AddQueryOption method to create a DataServiceQuery<TElement> class, which implements the IQueryable<T>

DataServiceQuery peopleQuery = dsc.People
    .AddQueryOption("$filter", "Gender eq Microsoft.OData.SampleService.Models.TripPin.PersonGender'Female'")
    .AddQueryOption("$skip", "3")
    .AddQueryOption("$orderby", "UserName desc");

foreach (Person person in peopleQuery)
{
    Console.WriteLine($"Username: {person.UserName} First Name: {person.FirstName} Gender: {person.Gender}");
}

In the case above, the URI that is generated by the OData client includes the requested entity set together with the added query options.

LINQ Query Methods

In the example below, we are creating a Linq query expression that returns only females, ordered by UserName. We skip the first 3 results and also specify which columns should be returned.

DefaultContainer dsc = new DefaultContainer(new Uri("https://services.odata.org/V4/(S(uvf1y321yx031rnxmcbqmlxw))/TripPinServiceRW/"));

var query = dsc.People.Where(p => p.Gender == PersonGender.Female)
    .OrderByDescending(p => p.UserName)
    .Skip(3)
    .Select(p => new { p.FirstName, p.LastName, p.UserName, p.Gender });

foreach(var person in query)
{
    Console.WriteLine($"Username: {person.UserName} First Name: {person.FirstName} Gender: {person.Gender}");
}

Since the DataServiceQuery<TElement> class implements the IQueryable<T> interface (System.Linq), the OData client library is able to translate Linq queries against entity sets into URIs executed against a data service resource.

The examples below demonstrate the kinds of LINQ queries that can be used to create various query options.

$filter

For GET https://host/service/People?$filter=FirstName eq 'Peter':

var people = context.People.Where(c => c.FirstName == "Peter");

For GET https://host/service/People?$filter=endswith(FirstName, 'Peter'):

var people = context.People.Where(c => c.FirstName.EndsWith("Peter"));

For GET https://host/service/People?$filter=Trips/$count eq 2:

var people = context.People.Where(c => c.Trips.Count == 2);

For GET https://host/service/People?$filter=Trips/any(d:d/Budget gt 6000):

var people = context.People.Where(c => c.Trips.Any(d => d.Budget > 6000));

For GET https://host/service/People?$filter=UserName in ('russellwhyte', 'scottketchum', 'ronaldmundy'):

var userNames = new List<string> { "russellwhyte", "scottketchum", "ronaldmundy" };
var people = context.People.Where(p => userNames.Contains(p.UserName));

$count

For GET https://host/service/People/$count:

var count = context.People.Count();

For GET https://host/service/People?$count=true:

We have two ways of making this request.

var people = context.People.IncludeCount();

var people = context.People.IncludeCount(true);

For GET https://host/service/People?$count=false:

var people = context.People.IncludeCount(false);

$orderby

For GET https://host/service/People?$orderby=FirstName:

var people = context.People.OrderBy(c => c.FirstName);

For GET https://host/service/People?$orderby=FirstName desc:

var people = context.People.OrderByDescending(c => c.FirstName);

For GET https://host/service/People?$orderby=Trips/$count:

var people = context.People.OrderBy(c => c.Trips.Count);

$skip

For GET https://host/service/People?$skip=3:

var people = context.People.Skip(3);

$top

For GET https://host/service/People?$top=3:

var people = context.People.Take(3);

$expand

For GET https://host/service/People?$expand=Trips:

var people = context.People.Expand(c => c.Trips);

$select

For GET https://host/service/People Selects all columns by default

For GET https://host/service/People?$select=* Same as above

var people = context.People;

For GET https://host/service/People?$select=FirstName,LastName:

var people = context.People.Select(c => new {c.FirstName, c.LastName});

A simple combined query combined

For GET https://host/service/People?$expand=Trips&$filter=FirstName eq 'Peter'&$orderby=Firstname asc&$skip=3&$top=3

var people =
    context.People
        .Expand(c => c.Trips)
        .Where(c => c.FirstName == "Peter")
        .OrderBy(c => c.FirstName)
        .Skip(3)
        .Take(3);

The order of the query options matters.

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