在C#中使用SQLite

SQLite 是一个嵌入式的关系数据库系统，使用十分广泛。在一些数据量不大的应用程序中，如果使用SQLite可以极大的减少部署时的工作量。 要在C#中使用SQLite也很简单，只要找一个C#的wrapper就可以了，例如，我使用的就是来自

http://sqlite.phxsoftware.com/  的一个dll，System.Data.SQLite. 下载下来的文件是SQLite-1.0.65.0-setup.exe。只要安装一下就可以使用了，非常方便。该程序符合ADO.NET的规范，并且支持Visual Studio的可视化表设计器。

打开Visual Studio 2008，新建一个Console Application，为此项目添加System.Data.SQLite的引用。添加一个数据库连接，此时可以发现，新建连接中有了一个SQLite Database Connection，选择此类型的数据连接，并且新建一个文件，

test.db3. 接下来在新数据库中添加一张表，如下：

下面开始为此表建立一个Data Access类，以展示在C#中如何使用SQLite，可以想象，和操作其他数据库是几乎一样的，感谢ADO.NET的功劳。

首先是一个实体类 Book.cs：

public class Book
    {
        private int id;
        private string bookName;
        private decimal price;

        public int ID
        {
            get { return id; }
            set { id = value; }
        }
        public string BookName
        {
            get { return bookName; }
            set { bookName = value; }
        }
        public decimal Price
        {
            get { return price; }
            set { price = value; }
        }
    }

编写DAL类：

using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SQLite;

namespace ConsoleApplication1
{
    public class BookDAL
    {
        public static bool Create(Book book)
        {
            try
            {
                using (SQLiteConnection conn = new SQLiteConnection("Data Source=e:\\test.db3"))
                {
                    conn.Open();
                    SQLiteCommand cmd = conn.CreateCommand();
                    cmd.CommandText = "insert into Book values(@ID,@BookName,@Price);";
                    cmd.Parameters.Add(new SQLiteParameter("ID", book.ID));
                    cmd.Parameters.Add(new SQLiteParameter("BookName", book.BookName));
                    cmd.Parameters.Add(new SQLiteParameter("Price", book.Price));
                    int i = cmd.ExecuteNonQuery();
                    return i == 1;
                }
            }
            catch (Exception)
            {
                //Do any logging operation here if necessary
                return false;
            }
        }

        public static bool Update(Book book)
        {
            try
            {
                using (SQLiteConnection conn = new SQLiteConnection("Data Source=e:\\test.db3"))
                {
                    conn.Open();
                    SQLiteCommand cmd = conn.CreateCommand();
                    cmd.CommandText = "update Book set BookName=@BookName,Price=@Price where ID=@ID;";
                    cmd.Parameters.Add(new SQLiteParameter("ID", book.ID));
                    cmd.Parameters.Add(new SQLiteParameter("BookName", book.BookName));
                    cmd.Parameters.Add(new SQLiteParameter("Price", book.Price));
                    int i = cmd.ExecuteNonQuery();
                    return i == 1;
                }
            }
            catch (Exception)
            {
                //Do any logging operation here if necessary
                return false;
            }
        }

        public static bool Delete(int ID)
        {
            try
            {
                using (SQLiteConnection conn = new SQLiteConnection("Data Source=e:\\test.db3"))
                {
                    conn.Open();
                    SQLiteCommand cmd = conn.CreateCommand();
                    cmd.CommandText = "delete from Book where ID=@ID;";
                    cmd.Parameters.Add(new SQLiteParameter("ID", ID));        
                    int i = cmd.ExecuteNonQuery();
                    return i == 1;
                }
            }
            catch (Exception)
            {
                //Do any logging operation here if necessary
                return false;
            }
        }

        public static Book GetbyID(int ID)
        {
            try
            {
                using (SQLiteConnection conn = new SQLiteConnection("Data Source=e:\\test.db3"))
                {
                    conn.Open();
                    SQLiteCommand cmd = conn.CreateCommand();
                    cmd.CommandText = "select * from Book where ID=@ID;";
                    cmd.Parameters.Add(new SQLiteParameter("ID", ID));
                    SQLiteDataReader dr = cmd.ExecuteReader();
                    if (dr.Read())
                    {
                        Book book = new Book();
                        book.ID = dr.GetInt32(0);
                        book.BookName = dr.GetString(1);
                        book.Price = dr.GetDecimal(2);
                        return book;
                    }
                    else
                        return null;
                }
            }
            catch (Exception)
            {
                //Do any logging operation here if necessary
                return null;
            }
        }
    }
}

编写测试主程序：

using System;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Book book = new Book();
            book.ID = 1;
            book.BookName = "Book A";
            book.Price = 10.0m;
            BookDAL.Create(book);

            book.ID = 2;
            book.BookName = "第二本书";
            book.Price = 13.0m;
            BookDAL.Create(book);

            book = BookDAL.GetbyID(2);
            Console.WriteLine(book.ID + " " + book.BookName + " " + book.Price);

            book.Price = 11.1m;
            BookDAL.Update(book);

            book = BookDAL.GetbyID(2);
            Console.WriteLine(book.ID + " " + book.BookName + " " + book.Price);
            book = BookDAL.GetbyID(1);
            Console.WriteLine(book.ID + " " + book.BookName + " " + book.Price);

        }
    }
}

最终结果：

2 第二本书 13
2 第二本书 11.1
1 Book A 10