LiteDB

LiteDB is a serverless database delivered in a single small DLL (< 450kb) fully written in .NET C# managed code (compatible with .NET 4.5 and NETStandard 2.0). Install it via NuGet or just copy the DLL to your bin project folder. LiteDB is a simple and fast NoSQL database solution. Ideal for mobile apps (Xamarin ready), desktop/local applications, application file format, web applications, and one database per account/user data store. Portable UWP and Xamarin iOS/Android, ACID transactions, single datafile (like SQLite), recovery data in writing failure (WAL mode), map your POCO class to BsonDocument, fluent API for custom mapping. Cross collections references (DbRef), store files and stream data (like GridFS in MongoDB), LINQ query support, free for everyone, including commercial use. LiteDB supports SQL-like language for data and structure manipulations. You can insert, update, delete or query your database using a very similar SQL relational language.