SQLite在C#中的应用

SQLite 是一个轻量级的嵌入式数据库，它适用于小型到中型的应用场景。SQLite在C#中的应用非常广泛，支持跨平台开发，并且非常易于使用。下面我们将详细介绍如何在C#中使用SQLite，并提供详细的例子。

特点

轻量级：SQLite 是一个嵌入式数据库，不需要独立的服务器进程，它是一个C库，可以集成到主程序中。
跨平台：SQLite 支持包括Windows、Linux、macOS在内的多个平台。
自包含：SQLite 的数据库是单个文件，非常适合移动应用和其他需要便携性的应用。
丰富的功能：支持事务、跨多个表的复杂查询、视图、触发器等。

环境配置

安装SQLite NuGet包

C#
dotnet add package System.Data.SQLite.Core

基础操作示例

1. 创建并连接SQLite数据库

首先，我们需要创建一个SQLite数据库，并连接到该数据库。

C#
private void btnCreateDb_Click(object sender, EventArgs e)
{
    string connectionString = "Data Source=demo.db;Version=3;";
    using (var connection = new SQLiteConnection(connectionString))
    {
        connection.Open();
        MessageBox.Show("SQLite database connection open.");
    }
}

2. 创建表

创建一个名为 users 的表，用于存储用户信息。

C#
private void btnCreateTable_Click(object sender, EventArgs e)
{
    string connectionString = "Data Source=demo.db;Version=3;";
    using (var connection = new SQLiteConnection(connectionString))
    {
        connection.Open();

        string sql = "CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)";
        using (var command = new SQLiteCommand(sql, connection))
        {
            command.ExecuteNonQuery();
            MessageBox.Show("Table 'users' created.");
        }
    }
}

3. 插入数据

往 users 表中插入用户数据。

C#
private void btnInsert_Click(object sender, EventArgs e)
{
    string connectionString = "Data Source=demo.db;Version=3;";
    using (var connection = new SQLiteConnection(connectionString))
    {
        connection.Open();

        string sql = "INSERT INTO users (name, age) VALUES ('Alice', 30)";
        using (var command = new SQLiteCommand(sql, connection))
        {
            command.ExecuteNonQuery();
            MessageBox.Show("Data inserted into 'users' table.");
        }
    }
}

4. 查询数据

从 users 表中查询数据，并打印输出。

C#
private void btnQuery_Click(object sender, EventArgs e)
{
    string connectionString = "Data Source=demo.db;Version=3;";
    using (var connection = new SQLiteConnection(connectionString))
    {
        connection.Open();

        string sql = "SELECT * FROM users";
        using (var command = new SQLiteCommand(sql, connection))
        {
            using (SQLiteDataReader reader = command.ExecuteReader())
            {
                while (reader.Read())
                {
                    MessageBox.Show($"ID: {reader["id"]}, Name: {reader["name"]}, Age: {reader["age"]}");
                }
            }
        }
    }
}

5. 更新数据

更新 users 表中的数据。

C#
using System;
using System.Data.SQLite;

class Program
{
    static void Main()
    {
        string connectionString = "Data Source=demo.db;Version=3;";
        using (var connection = new SQLiteConnection(connectionString))
        {
            connection.Open();

            string sql = "UPDATE users SET age = 31 WHERE name = 'Alice'";
            using (var command = new SQLiteCommand(sql, connection))
            {
                command.ExecuteNonQuery();
                Console.WriteLine("Data updated in 'users' table.");
            }
        }
    }
}

6. 删除数据

从 users 表中删除数据。

C#
using System;
using System.Data.SQLite;

class Program
{
    static void Main()
    {
        string connectionString = "Data Source=demo.db;Version=3;";
        using (var connection = new SQLiteConnection(connectionString))
        {
            connection.Open();

            string sql = "DELETE FROM users WHERE name = 'Alice'";
            using (var command = new SQLiteCommand(sql, connection))
            {
                command.ExecuteNonQuery();
                Console.WriteLine("Data deleted from 'users' table.");
            }
        }
    }
}

一个简单仓储类

用户模型类

C#
public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
}

我们创建一个用户仓储类，包含基本的CRUD（Create, Read, Update, Delete）操作：

C#
using System;
using System.Collections.Generic;
using System.Data.SQLite;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AppSqlLite
{
    public class UserRepository
    {
        private string _connectionString;

        public UserRepository(string connectionString)
        {
            _connectionString = connectionString;
            InitializeDatabase();
        }

        private void InitializeDatabase()
        {
            using (var connection = new SQLiteConnection(_connectionString))
            {
                connection.Open();

                string sql = "CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT, age INTEGER)";
                using (var command = new SQLiteCommand(sql, connection))
                {
                    command.ExecuteNonQuery();
                }
            }
        }

        public void AddUser(User user)
        {
            using (var connection = new SQLiteConnection(_connectionString))
            {
                connection.Open();

                string sql = "INSERT INTO users (name, age) VALUES (@name, @age)";
                using (var command = new SQLiteCommand(sql, connection))
                {
                    command.Parameters.AddWithValue("@name", user.Name);
                    command.Parameters.AddWithValue("@age", user.Age);
                    command.ExecuteNonQuery();
                }
            }
        }

        public User GetUser(int id)
        {
            using (var connection = new SQLiteConnection(_connectionString))
            {
                connection.Open();

                string sql = "SELECT * FROM users WHERE id = @id";
                using (var command = new SQLiteCommand(sql, connection))
                {
                    command.Parameters.AddWithValue("@id", id);
                    using (SQLiteDataReader reader = command.ExecuteReader())
                    {
                        if (reader.Read())
                        {
                            return new User
                            {
                                Id = Convert.ToInt32(reader["id"]),
                                Name = reader["name"].ToString(),
                                Age = Convert.ToInt32(reader["age"])
                            };
                        }
                    }
                }
            }
            return null;
        }

        public List<User> GetAllUsers()
        {
            List<User> users = new List<User>();
            using (var connection = new SQLiteConnection(_connectionString))
            {
                connection.Open();

                string sql = "SELECT * FROM users";
                using (var command = new SQLiteCommand(sql, connection))
                {
                    using (SQLiteDataReader reader = command.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            users.Add(new User
                            {
                                Id = Convert.ToInt32(reader["id"]),
                                Name = reader["name"].ToString(),
                                Age = Convert.ToInt32(reader["age"])
                            });
                        }
                    }
                }
            }
            return users;
        }

        public void UpdateUser(User user)
        {
            using (var connection = new SQLiteConnection(_connectionString))
            {
                connection.Open();

                string sql = "UPDATE users SET name = @name, age = @age WHERE id = @id";
                using (var command = new SQLiteCommand(sql, connection))
                {
                    command.Parameters.AddWithValue("@name", user.Name);
                    command.Parameters.AddWithValue("@age", user.Age);
                    command.Parameters.AddWithValue("@id", user.Id);
                    command.ExecuteNonQuery();
                }
            }
        }

        public void DeleteUser(int id)
        {
            using (var connection = new SQLiteConnection(_connectionString))
            {
                connection.Open();

                string sql = "DELETE FROM users WHERE id = @id";
                using (var command = new SQLiteCommand(sql, connection))
                {
                    command.Parameters.AddWithValue("@id", id);
                    command.ExecuteNonQuery();
                }
            }
        }
    }
}

C#
private void btnRepository_Click(object sender, EventArgs e)
{
    string connectionString = "Data Source=demo.db;Version=3;";
    UserRepository userRepository = new UserRepository(connectionString);

    // 添加用户
    User user = new User { Name = "Alice", Age = 30 };
    userRepository.AddUser(user);
    MessageBox.Show("User added.");

    // 获取用户
    User retrievedUser = userRepository.GetUser(1);
    MessageBox.Show($"Retrieved User: ID={retrievedUser.Id}, Name={retrievedUser.Name}, Age={retrievedUser.Age}");

    // 更新用户
    retrievedUser.Age = 31;
    userRepository.UpdateUser(retrievedUser);
    MessageBox.Show("User updated.");

    // 获取所有用户
    var users = userRepository.GetAllUsers();
    MessageBox.Show("All users:");
    foreach (var u in users)
    {
        MessageBox.Show($"ID={u.Id}, Name={u.Name}, Age={u.Age}");
    }

    // 删除用户
    userRepository.DeleteUser(1);
    MessageBox.Show("User deleted.");
}

结论

本文介绍了如何在C#中使用SQLite以及一些常见的数据库操作。SQLite 是一个强大的嵌入式数据库，适用于各种应用场景。希望通过本文的介绍，您能够轻松地在C#项目中使用SQLite进行数据库操作。

目录

特点