1. 在.net framework下设置Sqlite密码，访问数据，重设密码，删除密码。

using System;
using System.Data.SQLite;

namespace ConsoleApp1
{
    class Program
    {
        private const string password = "abc.123";
        static void Main(string[] args)
        {
            try
            {
                string dbFile = @"C:\repos\EFCoreDemos\EFCoreDemo1\Blogs.db";

                // 1. Set password for your DB
                using (SQLiteConnection conn = new SQLiteConnection("Data Source=" + dbFile+ ";Version=3;"))
                {
                    conn.Open();
                    conn.ChangePassword(password);
                }

                // 2. Access data 
                using (var conn2 = new SQLiteConnection("Data Source=" + dbFile + ";Version=3;Password=" + password))
                {
                    conn2.Open();
                    SQLiteCommand command = new SQLiteCommand("select * from blogs", conn2);
                    using (var reader = command.ExecuteReader())
                    {
                        while (reader.HasRows && reader.Read())
                        {
                            for (int i = 0; i < reader.FieldCount; i++)
                            {
                                Console.Write(reader[i] + ", ");
                            }
                            Console.WriteLine();
                        }
                    }
                }

                // 3. Clear db password
                using (SQLiteConnection conn = new SQLiteConnection("Data Source=" + dbFile + ";Version=3;Password=" + password))
                {
                    conn.Open();
                    conn.ChangePassword(string.Empty);
                }

                Console.ReadLine();
            }
            catch (Exception ex)
            {

            }
        }
    }
}

2. 在.net core目前不支持Sqlite密码相关的操作（甚至无法访问被密码加密的Sqlite数据库），但是可以使用以下方法Workaroud访问被密码加密的Sqlite数据库。请注意：这是在.net core下。

1) 设置一个扩展方法：

using System;
using System.Data.SQLite;

namespace EFCoreDemo1
{
    public static class SQLiteConnectionExtension
    {
        public static void SetPassword(this SQLiteConnection connection, string password)
        {
            if (connection.State != System.Data.ConnectionState.Open)
                throw new Exception("Open database first.");

            var cmd = connection.CreateCommand();
            cmd.CommandText = string.Format("PRAGMA key = '{0}'", password);
            cmd.ExecuteNonQuery();
        }
    }
}

2）使用这个扩展方法：

using System;
using System.Data.SQLite;

namespace EFCoreDemo1
{
    class Program
    {
        private const string password = @"abc.123";
        static void Main(string[] args)
        {
            try
            {
                string dbFile = @"C:\repos\EFCoreDemos\EFCoreDemo1\Blogs.db";
                using (SQLiteConnection conn = new SQLiteConnection("Data Source=" + dbFile))
                {
                    conn.Open();
                    conn.SetPassword(password);

                    SQLiteCommand command = new SQLiteCommand("select * from blogs", conn);
                    using (var reader = command.ExecuteReader())
                    {
                        while (reader.HasRows && reader.Read())
                        {
                            for (int i = 0; i < reader.FieldCount; i++)
                            {
                                Console.Write(reader[i] + ", ");
                            }
                            Console.WriteLine();
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                ;
            } 
        }
    }
}

参考：

1. https://stackoverflow.com/questions/39903863/password-protected-sqlite-with-entity-framework-core

2. https://stackoverflow.com/questions/1381264/password-protect-a-sqlite-db-is-it-possible