{"id":5003,"date":"2022-09-07T16:03:21","date_gmt":"2022-09-07T23:03:21","guid":{"rendered":"https:\/\/devblogs.microsoft.com\/odata\/?p=5003"},"modified":"2022-09-07T16:03:21","modified_gmt":"2022-09-07T23:03:21","slug":"extension-omit-null-value-properties-in-asp-net-core-odata","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/odata\/extension-omit-null-value-properties-in-asp-net-core-odata\/","title":{"rendered":"Extension: Omit null value properties in ASP.NET Core OData"},"content":{"rendered":"

Introduction<\/h2>\n

By default, ASP.NET Core OData serializes a single value property as \u201cnull\u201d, and a collection value property as an empty array if its value is null<\/strong> as such:<\/p>\n

{\r\n   \"SingleValueProperty\": null\r\n   \"CollectionValueProperty\": []\r\n}\r\n<\/pre>\n
It\u2019s good for most scenarios. However, omitting those ‘annoying<\/em>‘ null-value properties from the OData response gets more and more attention. Along with the latest ASP.NET Core OData, it\u2019s very easy to omit such null-value properties by extending the OData resource serializer. The approach is so common that it\u2019s better to create a post and value more customers\/developers. Let\u2019s get started.<\/p>\n
Prerequisites<\/h2>\n
As usual, my post starts with building an ASP.NET Core Web API application with Microsoft.AspNetCore.OData<\/a> (version-8.0.11) installed. You can follow up on my previous post to build the project.<\/p>\n
In the project, I create the following C# classes as the data model:<\/p>\n
<\/p>\n
Where:<\/p>\n
    \n
  1. School <\/strong>and Student <\/strong>are two entity types<\/li>\n
  2. Address<\/strong> is a complex type<\/li>\n
  3. Color<\/strong> is an enum type<\/li>\n<\/ol>\n
    The Edm model builder is as simple as the codes below:<\/p>\n
    public static IEdmModel GetEdmModel()\r\n{\r\n    var builder = new ODataConventionModelBuilder();\r\n    builder.EntitySet<School>(\"Schools\");\r\n    builder.EntitySet<Student>(\"Students\");\r\n    return builder.GetEdmModel();\r\n}\r\n<\/pre>\n
    I build the controller as below. As you can see, we can use attribute routing to specify multiple routes on one action.<\/p>\n
    [Route(\"odata\")]\r\npublic class SchoolStudentController : ODataController\r\n{\r\n    private readonly ISchoolStudentRepository _repo;\r\n\r\n    public SchoolStudentController(ISchoolStudentRepository repo)\r\n    {\r\n        _repo = repo;\r\n    }\r\n\r\n    [HttpGet(\"Schools\")]\r\n    [HttpGet(\"Schools\/{key}\")]\r\n    [EnableQuery]\r\n    public IActionResult GetSchool(int? key)\r\n    {\r\n        if (key != null)\r\n        {\r\n            return Ok(_repo.Schools.FirstOrDefault(s => s.ID == key.Value));\r\n        }\r\n        else\r\n        {\r\n            return Ok(_repo.Schools);\r\n        }\r\n    }\r\n\r\n    [HttpGet(\"Students\")]\r\n    [HttpGet(\"Students\/{key}\")]\r\n    [EnableQuery]\r\n    public IActionResult GetStudent(int? key)\r\n    {\r\n        \/\/ omit for similar codes\r\n    }\r\n<\/pre>\n
    Where:<\/p>\n
      \n
    1. GetSchool <\/strong>has the following two endpoints:\n