Build a C# application

Client driver: Npgsql

The following tutorial shows a small C# application that connects to a YugabyteDB cluster using the Npgsql driver and performs basic SQL operations. Use the application as a template to get started with YugabyteDB Aeon in C#.

Prerequisites

.NET 6.0 SDK or later.

Clone the application from GitHub

Clone the sample application to your computer:

git clone https://github.com/YugabyteDB-Samples/yugabyte-simple-csharp-app.git && cd yugabyte-simple-csharp-app

The yugabyte-simple-csharp-app.csproj file includes the following package reference to include the driver:

<PackageReference Include="npgsql" Version="6.0.3" />

Provide connection parameters

If your cluster is running on YugabyteDB Aeon, you need to modify the connection parameters so that the application can establish a connection to the YugabyteDB cluster. (You can skip this step if your cluster is running locally and listening on 127.0.0.1:5433.)

To do this:

  1. Open the sample-app.cs file.

  2. Set the following configuration-related parameters:

    • urlBuilder.Host - the host name of your YugabyteDB cluster. For local clusters, use the default (127.0.0.1). For YugabyteDB Aeon, select your cluster on the Clusters page, and click Settings. The host is displayed under Connection Parameters.
    • urlBuilder.Port - the port number for the driver to use (the default YugabyteDB YSQL port is 5433).
    • urlBuilder.Database - the name of the database you are connecting to (the default is yugabyte).
    • urlBuilder.Username and urlBuilder.Password - the username and password for the YugabyteDB database. For local clusters, use the defaults (yugabyte and yugabyte). For YugabyteDB Aeon, use the credentials in the credentials file you downloaded.
    • urlBuilder.SslMode - the SSL mode to use. YugabyteDB Aeon requires SSL connections; use SslMode.VerifyFull.
    • urlBuilder.RootCertificate - the full path to the YugabyteDB Aeon cluster CA certificate.

  3. Save the file.

Build and run the application

Build and run the application.

dotnet run

You should see output similar to the following:

>>>> Successfully connected to YugabyteDB!
>>>> Successfully created table DemoAccount.
>>>> Selecting accounts:
name = Jessica, age = 28, country = USA, balance = 10000
name = John, age = 28, country = Canada, balance = 9000
>>>> Transferred 800 between accounts.
>>>> Selecting accounts:
name = Jessica, age = 28, country = USA, balance = 9200
name = John, age = 28, country = Canada, balance = 9800

You have successfully executed a basic C# application that works with YugabyteDB Aeon.

Explore the application logic

Open the sample-app.cs file in the yugabyte-simple-csharp-app folder to review the methods.

connect

The connect method establishes a connection with your cluster via the Npgsql driver. To avoid making extra system table queries to map types, the ServerCompatibilityMode is set to NoTypeLoading.

NpgsqlConnectionStringBuilder urlBuilder = new NpgsqlConnectionStringBuilder();
urlBuilder.Host = "";
urlBuilder.Port = 5433;
urlBuilder.Database = "yugabyte";
urlBuilder.Username = "";
urlBuilder.Password = "";
urlBuilder.SslMode = SslMode.VerifyFull;
urlBuilder.RootCertificate = "";

urlBuilder.ServerCompatibilityMode = ServerCompatibilityMode.NoTypeLoading;

NpgsqlConnection conn = new NpgsqlConnection(urlBuilder.ConnectionString);

conn.Open();

createDatabase

The createDatabase method uses PostgreSQL-compliant DDL commands to create a sample database.

NpgsqlCommand query = new NpgsqlCommand("DROP TABLE IF EXISTS DemoAccount", conn);
query.ExecuteNonQuery();

query = new NpgsqlCommand("CREATE TABLE DemoAccount (" +
            "id int PRIMARY KEY," +
            "name varchar," +
            "age int," +
            "country varchar," +
            "balance int)", conn);
query.ExecuteNonQuery();

query = new NpgsqlCommand("INSERT INTO DemoAccount VALUES" +
            "(1, 'Jessica', 28, 'USA', 10000)," +
            "(2, 'John', 28, 'Canada', 9000)", conn);
query.ExecuteNonQuery();

selectAccounts

The selectAccounts method queries your distributed data using the SQL SELECT statement.

NpgsqlCommand query = new NpgsqlCommand("SELECT name, age, country, balance FROM DemoAccount", conn);

NpgsqlDataReader reader = query.ExecuteReader();

while (reader.Read())
{
    Console.WriteLine("name = {0}, age = {1}, country = {2}, balance = {3}",
        reader.GetString(0), reader.GetInt32(1), reader.GetString(2), reader.GetInt32(3));
}

transferMoneyBetweenAccounts

The transferMoneyBetweenAccounts method updates your data consistently with distributed transactions.

try
{
    NpgsqlTransaction tx = conn.BeginTransaction();

    NpgsqlCommand query = new NpgsqlCommand("UPDATE DemoAccount SET balance = balance - " +
        amount + " WHERE name = \'Jessica\'", conn, tx);
    query.ExecuteNonQuery();

    query = new NpgsqlCommand("UPDATE DemoAccount SET balance = balance + " +
        amount + " WHERE name = \'John\'", conn, tx);
    query.ExecuteNonQuery();

    tx.Commit();

    Console.WriteLine(">>>> Transferred " + amount + " between accounts");

} catch (NpgsqlException ex)
{
    if (ex.SqlState != null && ex.SqlState.Equals("40001"))
    {
        Console.WriteLine("The operation is aborted due to a concurrent transaction that is modifying the same set of rows." +
                "Consider adding retry logic for production-grade applications.");
    }

    throw ex;
}

Learn more

Npgsql driver