In this article we describe how to use JSON with Entity Framework Core and PostgreSQL, taking as reference the improved support since EF Core v7 for JSON data types, and how PostgreSQL has offered for years the json and jsonb types to store JSON documents in table columns.
PostgreSQL differentiates json and jsonb in storage mode and indexing capabilities: json is stored as-is as text, preserving field order and spaces, while jsonb is stored in binary format and facilitates the creation of indexes on JSON fields for fast queries.
To work with these types in a .Net Web API application, it is recommended to design the database table with dedicated columns for json and jsonb containing nested objects such as addresses, and from there map those columns to C# classes that represent the JSON objects. We do not include literal SQL statements here, but the idea is to have address columns of type json and addressb of type jsonb alongside common fields such as id, fullname, email, and createdAt.
In the EF Core data model, you can create classes like User and Address where User contains address and addressb properties of type Address. This way, EF Core will be able to automatically serialize and deserialize the nested objects when reading and writing to the JSON columns in PostgreSQL.
The DbContext configuration uses UseNpgsql for the PostgreSQL connection string. To map complex properties like Address to JSON columns, you can define the mapping in OnModelCreating using OwnsOne and the ToJson method to indicate that the property should be stored as JSON. With this configuration, it is possible to query internal JSON fields from LINQ, for example, filtering users by the postal code within addressb without writing native SQL.
Regarding the data access architecture, a useful approach is to implement a generic service for CRUD operations that receives the DbContext and offers reusable methods, and then build specific services like UserService that inherit from the generic service to expose methods used by the API controllers. Dependency injection in Program dot cs registers the DbContext and services so they are available at runtime.
Some practical points and best practices observed when implementing EF Core with PostgreSQL and JSON: the entity and table must have a primary key; in certain cases, annotations on properties can be used to specify the column type such as jsonb; for intensive queries on JSON fields, it is advisable to use jsonb and design appropriate indexes; and always test serialization and the JSON schema to avoid inconsistencies between the structure expected by the application and the stored data.
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Additional resources and a reference project example available at https://github.com/gaatif/pgsql-efcore-json to see a practical implementation. Contact Q2BSTUDIO for personalized advice on custom applications, custom software, artificial intelligence, cybersecurity, aws and azure cloud services, business intelligence services, AI agents, and power bi.
We hope this guide helps you understand how to map and query JSON data in PostgreSQL using EF Core and how your project can benefit from custom solutions integrated with AI and professional cloud services.
