Basic CRUD Operations

Artikel
12/09/2022

Applies To: # OData client v7 supported OData Client V7

Add an entity

var context = new DefaultContainer(new Uri("https://services.odata.org/V4/(S(y5tuj04bxbfsxzimbxbnauqg))/TripPinServiceRW/"));
    var person = Person.CreatePerson("russell", "Russell", "Whyte", new long());
    context.AddToPeople(person);

    context.SaveChanges();

Request an entity set

var context = new DefaultContainer(new Uri("https://services.odata.org/v4/(S(lqbvtwide0ngdev54adgc0lu))/TripPinServiceRW/"));

var people = context.People.Execute();

The Execute() API call will return an IEnumerable<Person>.

Request an individual entity

Either use the Where() API call:

var people = context.People.Where(c => c.UserName == "russellwhyte");
foreach (var person in people)
{
    // business logic
}

or use the Where() with First() or Single() API call:

var person = context.People.Where(c => c.UserName == "russellwhyte").First();
var person = context.People.Where(c => c.UserName == "russellwhyte").Single();

Note that First() will return one object, even if the lambda expression matches multiple objects. Single() always return one object and will throw an exception if the lambda expression matches multiple objects.

Both First() and Single() will throw an exception if no person with UserName as russelwhyte exists.

or use the ByKey() API:

var person = context.People.ByKey(userName: "russellwhyte").GetValue();

var person = context.People.ByKey(new Dictionary<string, object>() {{"UserName", "russellwhyte"}}).GetValue();

The person object returned are all of the type Person.

Update an entity

var context = new DefaultContainer(new Uri("https://services.odata.org/v4/(S(lqbvtwide0ngdev54adgc0lu))/TripPinServiceRW/"));

var person = context.People.ByKey(userName: "russellwhyte").GetValue(); // get an entity
person.FirstName = "Ross"; // change its property
context.UpdateObject(person); // create an update request

context.SaveChanges(); // send the request

Please be noted that the request is not sent until you call the SaveChanges() API. The context will track all the changes you make to the entities attached to it (by getting person from the service you attached it to the context) and will send requests for the changes when SaveChanges is called.

The sample above will send a PATCH request to the service in which the body is the whole Person containing properties that are unchanged. There is also a way to track the changes on the property level to only send changed properties in an update request. It will be introduced in later posts.

Delete an entity

var context = new DefaultContainer(new Uri("https://services.odata.org/v4/(S(lqbvtwide0ngdev54adgc0lu))/TripPinServiceRW/"));

var person = context.People.ByKey(userName: "russellwhyte").GetValue(); // get an entity
context.DeleteObject(person); // create a delete request

context.SaveChanges(); // send the request

Handling Exceptions in OData Client

OData Client has implemented a number of Exception classes including DataServiceQueryException and DataServiceClientException. Below is an example of how Exceptions can be handled while using OData Client.

 try
 {
    //Code that throws exception from the service
 }
 catch (DataServiceQueryException ex)
 {
     //Client level Exception message
     Console.WriteLine(ex.Message);

     //The InnerException of DataServiceQueryException contains DataServiceClientException
     DataServiceClientException dataServiceClientException = ex.InnerException as DataServiceClientException;
     Console.WriteLine(dataServiceClientException.Message);

     // You can get ODataErrorException from dataServiceClientException.InnerException
     // This object holds Exception as thrown from the service
     // ODataErrorException contains odataErrorException.Message contains a message string that conforms to dotnet
     // Exception.Message standards
     ODataErrorException odataErrorException = dataServiceClientException.InnerException as ODataErrorException;
     
     if(odataErrorException != null)
     {
       Console.WriteLine(odataErrorException.Message);
     }  
 }

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