Build a C# application

• YCQL
• YSQL

Prerequisites

This tutorial assumes that you have:

• installed YugabyteDB, created a universe and are able to interact with it using the CQL shell. If not, please follow these steps in the quick start guide.
• installed Visual Studio

Writing a HelloWorld C# app

In your Visual Studio create a new Project and choose Console Application as template. Follow the instructions to save the project.

Install YugaByteCassandraCSharpDriver C# driver

YugabyteDB has forked the Cassandra driver to add more features like JSONB and change the routing policy.Install the C# driver in your Visual Studio project byfollowing instructions on the page.

Copy the contents below to your Program.cs file.

using System;
using System.Linq;
using Cassandra;
namespace Yugabyte_CSharp_Demo
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                var cluster = Cluster.Builder()
                                     .AddContactPoints("127.0.0.1")
                                     .WithPort(9042)
                                     .Build();
                var session = cluster.Connect();
                session.Execute("CREATE KEYSPACE IF NOT EXISTS ybdemo");
                Console.WriteLine("Created keyspace ybdemo");
                var createStmt = "CREATE TABLE IF NOT EXISTS ybdemo.employee(" +
                    "id int PRIMARY KEY, name varchar, age int, language varchar)";
                session.Execute(createStmt);
                Console.WriteLine("Created keyspace employee");
                var insertStmt = "INSERT INTO ybdemo.employee(id, name, age, language) " +
                    "VALUES (1, 'John', 35, 'C#')";
                session.Execute(insertStmt);
                Console.WriteLine("Inserted data: {0}", insertStmt);
                var preparedStmt = session.Prepare("SELECT name, age, language " +
                                                   "FROM ybdemo.employee WHERE id = ?");
                var selectStmt = preparedStmt.Bind(1);
                var result = session.Execute(selectStmt);
                var rows = result.GetRows().ToList();
                Console.WriteLine("Select query returned {0} rows", rows.Count());
                Console.WriteLine("Name\tAge\tLanguage");
                foreach (Row row in rows)
                    Console.WriteLine("{0}\t{1}\t{2}", row["name"], row["age"], row["language"]);
                session.Dispose();
                cluster.Dispose();
            }
            catch (Cassandra.NoHostAvailableException)
            {
                Console.WriteLine("Make sure YugabyteDB is running locally!.");
            }
            catch (Cassandra.InvalidQueryException ie)
            {
                Console.WriteLine("Invalid Query: " + ie.Message);
            }
        }
    }
}

Running the C# app

Run the C# app from menu select Run -> Start Without Debugging

You should see the following as the output.

Created keyspace ybdemo
Created keyspace employee
Inserted data: INSERT INTO ybdemo.employee(id, name, age, language) VALUES (1, 'John', 35, 'C#')
Select query returned 1 rows
Name    Age Language
John    35  C#

Prerequisites

This tutorial assumes that you have:

• installed YugabyteDB, created a universe, and are able to interact with it using the YSQL shell. If not, please follow these steps in the ysql guide.
• installed Visual Studio

Writing a HelloWorld C# application

In your Visual Studio, create a new Project and choose Console Application as template. Follow the instructions to save the project.

Install YSQL C# driver

To install the driver in your Visual Studio project:

• Open your Project Solution View.
• Right-click on Packages and click Add Packages.
• Search for Npgsql and click Add Package.

Copy the contents below to your Program.cs file

using System;
using Npgsql;
namespace Yugabyte_CSharp_Demo
{
    class Program
    {
        static void Main(string[] args)
        {
            NpgsqlConnection conn = new NpgsqlConnection("host=localhost;port=5433;database=yb_demo;user id=yugabyte;password=");
            try
            {
                conn.Open();
                NpgsqlCommand empCreateCmd = new NpgsqlCommand("CREATE TABLE employee (id int PRIMARY KEY, name varchar, age int, language varchar);", conn);
                empCreateCmd.ExecuteNonQuery();
                Console.WriteLine("Created table Employee");
                NpgsqlCommand empInsertCmd = new NpgsqlCommand("INSERT INTO employee (id, name, age, language) VALUES (1, 'John', 35, 'CSharp');", conn);
                int numRows = empInsertCmd.ExecuteNonQuery();
                Console.WriteLine("Inserted data (1, 'John', 35, 'CSharp')");
                NpgsqlCommand empPrepCmd = new NpgsqlCommand("SELECT name, age, language FROM employee WHERE id = @EmployeeId", conn);
                empPrepCmd.Parameters.Add("@EmployeeId", NpgsqlTypes.NpgsqlDbType.Integer);
                empPrepCmd.Parameters["@EmployeeId"].Value = 1;
                NpgsqlDataReader reader = empPrepCmd.ExecuteReader();
                Console.WriteLine("Query returned:\nName\tAge\tLanguage"); 
                while (reader.Read())
                {
                    Console.WriteLine("{0}\t{1}\t{2}", reader.GetString(0), reader.GetInt32(1), reader.GetString(2));
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("Failure: " + ex.Message);
            }
            finally
            {
                if (conn.State != System.Data.ConnectionState.Closed)
                {
                    conn.Close();
                }
            }
        }
    }
}

Running the C# application

Run the C# app from menu select Run -> Start Without Debugging

You should see the following as the output.

Created table Employee
Inserted data (1, 'John', 35, 'CSharp')
Query returned:
Name    Age Language
John    35  CSharp