![\"JSON](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/a-picture-containing-text-screenshot-font-numbe-1.png\")
<\/p>\n
OData library, by default, uses the plain text JSON representation for OData requests and response data serialization (writing) and deserialization (reading). But it\u2019s also designed to enable developers to customize other JSON representations. I’d use this post to share with you the process to enable CBOR representation serialization and deserialization using ASP.NET Core OData. Let\u2019s get started.<\/p>\n
Prerequisites<\/h2>\n
Let\u2019s start to create an ASP.NET Core Web API application named ODataCborExample<\/em><\/strong>\u00a0with Microsoft.AspNetCore.OData<\/a>\u00a0(version-8.0.12) installed. For simplicity, I reuse the \u2018Book\u2019<\/strong> entity and its controller from this<\/a> post. I\u2019m omitting those codes in this post and please refer to here<\/a> for detailed implementations.<\/p>\n I need a library to finish the CBOR binary data reading and writing. You can find various implementations of CBOR for most computer languages from here<\/a>. In this post, I choose to use System.Formats.Cbor<\/strong>, since it\u2019s the built-in solution for .Net and everyone can install\/consume this package from Nuget.org<\/a>. Here’s ODataCborExample<\/em><\/strong> project configuration:<\/p>\n System.Formats.Cbor<\/strong> provides CborWriter<\/a><\/strong> to finish CBOR encoded JSON binary writing. To inject CborWriter<\/strong> into OData JSON serialization, we should customize an OData JSON writer to use it.<\/p>\n The OData JSON serialization process relies on two interfaces:<\/p>\n Let\u2019s create the following class named CborODataWriter<\/strong> which implements the above two interfaces as below:<\/p>\n The constructor of CborODataWriter<\/strong> accepts the writing stream, an encoding and Ieee754Compatible<\/em> Boolean value (the last two are not used in this post for simplicity) and creates an instance of System.Formats.Cbor.CborWriter<\/strong>.<\/p>\n We must implement the methods defined in the OData JSON writer interface. The implementation is straightforward as:<\/p>\n We simply delegate each writing action in CborODataWriter<\/strong> to the corresponding writing method in CborWriter<\/strong> since CBOR is the binary representation of JSON.<\/p>\n Here\u2019s a simple mapping table for your reference between OData JSON writing methods and CBOR writing methods:<\/p>\n![](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/word-image-5215-2-1.png\")
<\/p>\nCBOR serialization<\/h2>\n
CBOR OData JSON writer<\/h2>\n
\n
using System.Formats.Cbor;\r\n\r\npublic partial class CborODataWriter : IJsonWriter, IJsonWriterAsync\r\n{\r\n private CborWriter _cborWriter;\r\n private Stream _stream;\r\n private bool _isIeee754Compatible;\r\n private Encoding _encoding;\r\n\r\n public CborODataWriter(Stream stream, bool isIeee754Compatible, Encoding encoding)\r\n {\r\n _stream = stream;\r\n _isIeee754Compatible = isIeee754Compatible;\r\n _encoding = encoding;\r\n _cborWriter = new CborWriter();\r\n }\r\n}\r\n<\/pre>\npublic partial class CborODataWriter : IJsonWriter, IJsonWriterAsync\r\n{\r\n \/\/ \u2026\u2026\r\n public void StartArrayScope()\r\n {\r\n _cborWriter.WriteStartArray(null);\r\n }\r\n\r\n public void StartObjectScope()\r\n {\r\n _cborWriter.WriteStartMap(null);\r\n }\r\n\r\n public void EndArrayScope()\r\n {\r\n _cborWriter.WriteEndArray();\r\n }\r\n\r\n public void EndObjectScope()\r\n {\r\n _cborWriter.WriteEndMap();\r\n }\r\n\r\n public void WriteValue(bool value)\r\n {\r\n _cborWriter.WriteBoolean(value);\r\n }\r\n\r\n \/\/ \u2026\u2026 Omit other writing methods.\r\n public Task StartArrayScopeAsync()\r\n {\r\n StartArrayScope();\r\n return Task.CompletedTask;\r\n }\r\n\r\n public Task StartObjectScopeAsync()\r\n {\r\n StartObjectScope();\r\n return Task.CompletedTask;\r\n }\r\n\r\n \/\/ \u2026\u2026 omit other async methods.\r\n}\r\n<\/pre>\n
![\"Graphical](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/graphical-user-interface-text-application-email-6.png\")
<\/p>\n![](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/cbor_book_1.png\")
<\/p>\n![\"benchmark\"](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/cbor_mechmark_png.png\")
<\/p>\n![\"binary](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/a-picture-containing-text-font-screenshot-numbe-2.png\")
<\/p>\n![\"VS](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/graphical-user-interface-text-application-descr-2.png\")
<\/p>\n![](\"https:\/\/devblogs.microsoft.com\/odata\/wp-content\/uploads\/sites\/23\/2023\/03\/word-image-5215-7-1.png\")
<\/p>\n