csharp [DB接続] SQL Serverへの接続~CRUD操作

Posted 2021-05-12

using System;
using System.Text;
using System.Data.SqlClient;

namespace DatabaseSample
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                Console.WriteLine("Connect to SQL Server and Create, Read, Update and Delete operations.");

                SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder()
                {
                    DataSource = @"localhost",
                    //IntegratedSecurity = true,
                    UserID = "sa",
                    Password = "your_password",
                    InitialCatalog = "master"
                };

                Console.Write("Connecting to SQL Server ... ");
                using (SqlConnection connection = new SqlConnection(builder.ConnectionString))
                {
                    connection.Open();
                    Console.WriteLine("Done.");
                    // Create a sample database
                    CreateDatabase(connection);
                    // Create a Table and insert some sample data.
                    CreateTable(connection);
                    // INSERT demo
                    Insert(connection);
                    // UPDATE demo
                    Update(connection);
                    // DELETE demo
                    Delete(connection);
                    // READ demo
                    Select(connection);
                }
            }
            catch (SqlException e)
            {
                Console.WriteLine(e.ToString());
            }

            Console.WriteLine("All done. Press any key to finish...");
            Console.ReadKey(true);
        }

        private static void Select(SqlConnection connection)
        {
            Console.WriteLine("Reading data from table, press any key to continue...");
            Console.ReadKey(true);
            StringBuilder sb = new StringBuilder();
            sb.Append("SELECT Id, Name, Location FROM Employees ");
            var sql = sb.ToString();
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        Console.WriteLine("{0} {1} {2}", reader.GetInt32(0), reader.GetString(1), reader.GetString(2));
                    }
                }
            }
        }

        private static void Delete(SqlConnection connection)
        {
            string userToDelete = "Jared";
            Console.WriteLine($"Deleting user '{userToDelete}', press any key to continue...");
            Console.ReadKey(true);
            StringBuilder sb = new StringBuilder();
            sb.Append("DELETE FROM Employees WHERE Name = @name ");
            var sql = sb.ToString();
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                command.Parameters.AddWithValue("@name", userToDelete);
                int rowsAffected = command.ExecuteNonQuery();
                Console.WriteLine($"{rowsAffected} row(s) deleted");
            }
        }

        private static void Update(SqlConnection connection)
        {
            string userToUpdate = "Nikita";
            Console.WriteLine($"Updating 'Location' for user '{userToUpdate}', press any key to continue...");
            Console.ReadKey(true);
            StringBuilder sb = new StringBuilder();
            sb.Append("UPDATE Employees SET Location = N'United States' WHERE Name = @name ");
            var sql = sb.ToString();
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                command.Parameters.AddWithValue("@name", userToUpdate);
                int rowsAffected = command.ExecuteNonQuery();
                Console.WriteLine($"{rowsAffected} row(s) updated");
            }
        }

        private static void Insert(SqlConnection connection)
        {
            Console.WriteLine("Inserting a new row into table, press any key to continue...");
            Console.ReadKey(true);
            StringBuilder sb = new StringBuilder();
            sb.Append("INSERT INTO Employees (Name, Location) ");
            sb.Append("VALUES (@name, @location) ");
            var sql = sb.ToString();
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                command.Parameters.AddWithValue("@name", "Jake");
                command.Parameters.AddWithValue("@location", "United States");
                int rowsAffected = command.ExecuteNonQuery();
                Console.WriteLine($"{rowsAffected} row(s) inserted");
            }
        }

        private static void CreateTable(SqlConnection connection)
        {
            Console.WriteLine("Creating sample table with data, press any key to continue...");
            Console.ReadKey(true);
            StringBuilder sb = new StringBuilder();
            sb.Append("USE SampleDB; ");
            sb.Append("CREATE TABLE Employees ( ");
            sb.Append(" Id INT IDENTITY(1,1) NOT NULL PRIMARY KEY, ");
            sb.Append(" Name NVARCHAR(50), ");
            sb.Append(" Location NVARCHAR(50) ");
            sb.Append("); ");
            sb.Append("INSERT INTO Employees (Name, Location) VALUES ");
            sb.Append("(N'Jared', N'Australia'), ");
            sb.Append("(N'Nikita', N'India'), ");
            sb.Append("(N'Tom', N'Germany') ");
            var sql = sb.ToString();
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                command.ExecuteNonQuery();
                Console.WriteLine("Done.");
            }
        }

        private static void CreateDatabase(SqlConnection connection)
        {
            Console.WriteLine("Dropping and creating database 'SampleDB' ... ");
            StringBuilder sb = new StringBuilder();
            sb.Append("DROP DATABASE IF EXISTS [SampleDB]; ");
            sb.Append("CREATE DATABASE [SampleDB]");
            var sql = sb.ToString();
            using (SqlCommand command = new SqlCommand(sql, connection))
            {
                command.ExecuteNonQuery();
                Console.WriteLine("Done.");
            }
        }
    }
}