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• 本文详细介绍了SQLite实现CodeFirst的方式
• 通过代码配合图文的形式进行讲解
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本文所介绍的是真正的EF+CodeFirst，不需要提前建表，由代码自动生成！

一、提前准备

1 下载Sqlite Expert

下载Sqlite Expert

下载免费版个人版就够用了

• 下载后新建数据库，然后保存到你指定的目录即可（保存为.db文件）

2 安装VS扩展工具

• 然后在VS中->工具->扩展和更新->联机

• 搜索SQLite/SQL Server Compact ToolBox ，下载完后重启VS

• 在同一个地方再搜索dotConnect ADO.NET Data Provider for SQLite，记得不是安装Standard的，点下载后会出现个弹出框下载，下载完后安装时要先关闭VS

二、项目接入

1 先在NuGet中添加相关依赖项

• SQLite和SQLite.CodeFirst

2 定义实体类

public class Student
{
    public int ID { get; set; }

    public string Name { get; set; }

    public int Age { get; set; }

    public string Gender { get; set; }
}

3 添加Context类

• 继承自DbContext以及Model配置类

public class StudentContext : DbContext
{
    //定义属性，便于外部访问数据表
    public DbSet<Student> Students { get { return Set<Student>(); } }

    public StudentContext() : base("dbConn")
    {

    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        ModelConfiguration.Configure(modelBuilder);
        var init = new SqliteDropCreateDatabaseWhenModelChanges<StudentContext>(modelBuilder);
        //var init = new SqliteCreateDatabaseIfNotExists<MyBookDB>(modelBuilder);
        Database.SetInitializer(init);
    }
}

public class ModelConfiguration
{
    public static void Configure(DbModelBuilder modelBuilder)
    {
        ConfigureBookEntity(modelBuilder);
    }
    private static void ConfigureBookEntity(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Student>();
    }
}

4 获取数据库连接字符串

• 工具->连接到数据库->更改->选择SQLite Database->Browse数据库文件->测试成功后复制Connection String

5 修改配置文件APP.config

• 在</system.data>结点后面添加连接字符串

  <connectionStrings>
    <add name="SQLiteConnect" connectionString="Data Source=F:\xxx\SQLLiteTest.db" providerName="System.Data.SQLite.EF6"/>
  </connectionStrings>

• 添加Provider结点（主要原因是SQLite的invarianName不是在自动生成的.EF6里面）

<provider invariantName="System.Data.SQLite" type="System.Data.SQLite.EF6.SQLiteProviderServices, System.Data.SQLite.EF6" />

三、验证测试

1 界面窗口布局

2 按钮事件

private void btnAdd_Click(object sender, EventArgs e)
{
    List<Student> books = new List<Student>()
    {
        new Student() {ID=1, Name = "小明", Age = 11, Gender = "男" },
        new Student() {ID=2, Name = "老王",  Age = 12, Gender = "男" },
        new Student() {ID=3, Name = "小郭", Age = 10, Gender = "女" },
        new Student() {ID=4, Name = "小李",  Age = 11, Gender = "男" },
        new Student() {ID=5, Name = "小玉",  Age = 9, Gender = "女" },
    };

    using (var db = new StudentContext())
    {
        db.Students.AddRange(books);
        int count = db.SaveChanges();
        this.Text = $"{DateTime.Now}, 插入{count}条记录";
    }
}
private void btnModify_Click(object sender, EventArgs e)
{
    using (var db = new StudentContext())
    {
        var students = db.Students.FirstOrDefault(x => x.Name == "小李");
        if (students != null)
        {
            students.Age += 1;
            int count = db.SaveChanges();
            this.Text = $"{DateTime.Now}, 修改{count}条记录";
        }
    }
}

private void btnDel_Click(object sender, EventArgs e)
{
    using (var db = new StudentContext())
    {
        var students = db.Students.FirstOrDefault(x => x.Name == "小玉");
        if (students != null)
        {
            var result = db.Students.Remove(students);
            int count = db.SaveChanges();
            this.Text = $"{DateTime.Now}, 删除{count}条记录";
        }
    }
}

private void btnQuery_Click(object sender, EventArgs e)
{
    using (var db = new StudentContext())
    {
        var students = db.Students.Where(x => x.Name == "老王").OrderByDescending(x => x.Age).ToList();
        this.Text = $"{DateTime.Now}, 查到{students.Count}条记录";
        this.dataGridView1.DataSource = students;
    }
}

private void btnRefresh_Click(object sender, EventArgs e)
{
    using (var db = new StudentContext())
    {
        var students = db.Students.ToList();
        this.dataGridView1.DataSource = students;
    }
}

3 效果

• 根据代码生成表