使用System.Data.SQLite及其EF模块操作SQLite数据库（文件）

• SQLite for .NET (System.Data.SQLite)
  • introduction
  • An ADO.NET provider for SQLite including EF and Linq functions.
  • http://system.data.sqlite.org/index.html/doc/trunk/www/index.wiki
  • Developed by SQLite Development Team
  • License: Public Domain, Open-Source, not Open-Contribution
  • how to use
    • Add references (Nuget to find “System.Data.SQLite”)
      • EntityFramework (can be upgraded to 6.2.0, already include EF and Linq)
      • System.Data.SQLite
      • System.Data.SQLite.Core
      • System.Data.SQLite.EF6 (can be removed)
      • System.Data.SQLite.Linq (can be removed)
    • Setup configuration file (in App.config)
      • connection string
      • db provider
    • Create custom context class

在App.Config或Web.config文件中配置数据库的连接字符串及使用到的Provider：

 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
   <configSections>
     <!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 -->
     <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false"/>
   </configSections>
   <connectionStrings>
     <add name="PresetDataConnectionString" connectionString="data source=PresetData.db" providerName="System.Data.SQLite"/>
   </connectionStrings>
   <entityFramework>
     <defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
       <parameters>
         <parameter value="v13.0"/>
       </parameters>
     </defaultConnectionFactory>
     <providers>
       <provider invariantName="System.Data.SQLite" type="System.Data.SQLite.EF6.SQLiteProviderServices, System.Data.SQLite.EF6"/>
     </providers>
   </entityFramework>
   <system.data>
     <DbProviderFactories>
       <remove invariant="System.Data.SQLite"/>
       <add name="SQLite Data Provider" invariant="System.Data.SQLite" description=".NET Framework Data Provider for SQLite" type="System.Data.SQLite.SQLiteFactory, System.Data.SQLite"/>
     </DbProviderFactories>
   </system.data>
   <startup>
     <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.2"/>
   </startup>
 </configuration>

自定义Context类，用于操作数据库：

     /// <summary>
     /// Code First mode to use EF, on behalf of one DB
     /// </summary>
     public class UserDataContext : DbContext
     {
         public DbSet<FavoriteData> FavoriteDatas { get; set; }

         public UserDataContext(string connectionString)
             : base(new SQLiteConnection() { ConnectionString = connectionString }, true)
         {

         }

         /// <summary>
         /// avoid "no such table error" of __MigrationHistory and EdmMetadata in EF Code-First Mode
         /// </summary>
         static UserDataContext()
         {
             Database.SetInitializer<PresetDataContext>(null);
         }

         /// <summary>
         /// dummy code so that the compiler would detect that the reference is being used.
         /// make sure projects like VisualXml and VisualXml.Test have related dlls in output bin folder
         /// </summary>
         private static void FixProvidersNotAutoLoadProblem()
         {
             var _ = typeof(System.Data.SQLite.EF6.SQLiteProviderFactory);
             var __ = typeof(System.Data.SQLite.SQLiteFactory);
             //var ___ = typeof(System.Data.Entity.SqlServer.SqlProviderServices);
         }

         /// <summary>
         /// remove restriction of DbSet field names based on table names
         /// </summary>
         /// <param name="modelBuilder"></param>
         protected override void OnModelCreating(DbModelBuilder modelBuilder)
         {
             modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();

             //modelBuilder.Configurations.AddFromAssembly(typeof(DefaultContext).Assembly);
             //modelBuilder.Configurations.AddFromAssembly(Assembly.GetExecutingAssembly());
         }
     }

也可以动态设置数据库连接字符串（动态往自定义的Context类的构造函数中传入拼接的连接字符串，userDataDBFilePath为db文件物理路径）：

             SQLiteConnectionStringBuilder builder = SQLiteFactory.Instance.CreateConnectionStringBuilder() as SQLiteConnectionStringBuilder;

             // set up connection string for user data db in code
             builder.DataSource = userDataDBFilePath;
             builder.Password = GenerateEncryptedDBPwd();
             UserDataContext userDataDB = new UserDataContext(builder.ToString());

也可以直接使用ADO.NET操作数据库：

                SQLiteConnectionStringBuilder builder = SQLiteFactory.Instance.CreateConnectionStringBuilder() as SQLiteConnectionStringBuilder;
                builder.DataSource = "PresetData.db";
                using (SQLiteConnection conn = new SQLiteConnection(builder.ToString()))
                {
                    conn.Open();
                    string currentLanguageViewName = "vw_nc_variable_entire_info_" + Thread.CurrentThread.CurrentUICulture.Name.ToLowerInvariant().Replace('-', '_');
                    string sql = "select count(*) from sqlite_master where type = 'table' and name = '{" + currentLanguageViewName + "}'";
                    SQLiteCommand cmd = new System.Data.SQLite.SQLiteCommand();
                    cmd.CommandText = sql;
                    cmd.Connection = conn;
                    int tableInfoCount = Convert.ToInt32(cmd.ExecuteScalar());
                    )
                    {
                        modelBuilder.Entity<EntireInfo>().ToTable("vw_nc_variable_entire_info_" + Thread.CurrentThread.CurrentUICulture.Name.ToLowerInvariant().Replace('-', '_'));
                    }
                    else
                    {
                        modelBuilder.Entity<EntireInfo>().ToTable("vw_nc_variable_entire_info_en_us");
                    }
                    conn.Close();
                }