Example app in C# (.NET)

This page contains a detailed description of the code of a test app that uses the YDB C# (.NET) SDK.

Initializing a database connection

To interact with YDB, create instances of the driver, client, and session:

  • The YDB driver facilitates interaction between the app and YDB nodes at the transport layer. It must be initialized before creating a client or session and must persist throughout the YDB access lifecycle.
  • The YDB client operates on top of the YDB driver and enables the handling of entities and transactions.
  • The YDB session, which is part of the YDB client context, contains information about executed transactions and prepared queries.

App code snippet for connecting to the database:

using Ydb.Sdk.Ado;

await using var dataSource = new YdbDataSource("Host=localhost;Port=2136;Database=/local");
await using var connection = await dataSource.OpenConnectionAsync();

Creating tables

Create tables to be used in operations on a test app. This step results in the creation of database tables for the series directory data model:

  • Series
  • Seasons
  • Episodes

After the tables are created, a method for retrieving information about data schema objects is called, and the result of its execution is displayed.

To create tables, use YdbCommand with a DDL (Data Definition Language) YQL query:

await using var command = new YdbCommand(connection)
{
    CommandText = @"
        CREATE TABLE series (
            series_id Uint64 NOT NULL,
            title Utf8,
            series_info Utf8,
            release_date Date,
            PRIMARY KEY (series_id)
        );

        CREATE TABLE seasons (
            series_id Uint64,
            season_id Uint64,
            title Utf8,
            first_aired Date,
            last_aired Date,
            PRIMARY KEY (series_id, season_id)
        );

        CREATE TABLE episodes (
            series_id Uint64,
            season_id Uint64,
            episode_id Uint64,
            title Utf8,
            air_date Date,
            PRIMARY KEY (series_id, season_id, episode_id)
        );"
};
await command.ExecuteNonQueryAsync();

Adding data

Add data to the created tables using the UPSERT statement in YQL. A data update request is sent to the server as a single request with transaction auto-commit mode enabled.

Code snippet for data insert/update:

await using var command = new YdbCommand(@"
    UPSERT INTO series (series_id, title, release_date) VALUES
        ($id, $title, $release_date);
    ", connection);
command.Parameters.Add(new YdbParameter("$id", YdbDbType.Uint64, 1UL));
command.Parameters.Add(new YdbParameter("$title", YdbDbType.Text, "NewTitle"));
command.Parameters.Add(new YdbParameter("$release_date", YdbDbType.Date, DateTime.UtcNow));
await command.ExecuteNonQueryAsync();

Retrieving data

Retrieve data using a SELECT statement in YQL. Handle the retrieved data selection in the app.

To read data with a YQL query, use the ExecuteReaderAsync method. Query parameters are passed through the Parameters collection of the YdbCommand object:

await using var command = new YdbCommand(@"
    SELECT
        series_id,
        title,
        release_date
    FROM series
    WHERE series_id = $id;
    ", connection);
command.Parameters.Add(new YdbParameter("$id", YdbDbType.Uint64, id));
await using var reader = await command.ExecuteReaderAsync();

Processing execution results

The query result is processed via DbDataReader. Example of processing the result:

while (await reader.ReadAsync())
{
    Console.WriteLine($"> Series, " +
        $"series_id: {reader.GetUint64(0)}, " +
        $"title: {reader.GetString(1)}, " +
        $"release_date: {reader.GetDateTime(2)}");
}

For sequential row reading from another query:

await using var command = new YdbCommand(
    "SELECT title FROM seasons ORDER BY series_id, season_id;", connection);
await using var reader = await command.ExecuteReaderAsync();
while (await reader.ReadAsync())
{
    Console.WriteLine(reader.GetString(0));
}
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