Project: YugabyteDB (App Definition and Development / Database)
File: cloud-ysql-csharp.md

title: Build a C# application using the Npgsql driver headerTitle: Build a C# application description: Build a small C# application using the Npgsql driver and using the YSQL API to connect to and interact with a YugabyteDB Managed cluster. headContent: "Client driver: Npgsql" menu: v2.18: parent: build-apps name: C# identifier: cloud-csharp weight: 600 type: docs The following tutorial shows a small that connects to a YugabyteDB cluster using the and performs basic SQL operations. Use the application as a template to get started with YugabyteDB Managed in C#. or later. Clone the sample application to your computer: ```sh 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: ```cpp <PackageReference Include="npgsql" Version="6.0.3" /> ``` If your cluster is running on YugabyteDB Managed, 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: Open the `sample-app.cs` file. 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 Managed, 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 Managed, use the credentials in the credentials file you downloaded. urlBuilder.SslMode - the SSL mode to use. YugabyteDB Managed ; use `SslMode.VerifyFull`. urlBuilder.RootCertificate - the full path to the YugabyteDB Managed cluster CA certificate. Save the file. Build and run the application. ```sh dotnet run ``` You should see output similar to the following: ```output >>> Successfully connected to YugabyteDB! >>> Successfully created table

>>> 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 Managed. Open the `sample-app.cs` file in the `yugabyte-simple-csharp-app` folder to review the methods. 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`. ```cpp 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(); ``` The `createDatabase` method uses PostgreSQL-compliant DDL commands to create a sample database. ```cpp 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(); ``` The `selectAccounts` method queries your distributed data using the SQL `SELECT` statement. ```cpp 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)); } ``` The `transferMoneyBetweenAccounts` method updates your data consistently with distributed transactions. ```cpp 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; } ```