Entity Framework 6 SQL 服务器上的代码优先：将 "bool" 映射到 "numeric(1,0)" 而不是 "bit"

Question

转发警告 #0：在不久的将来升级到 EF 核心不是一个选项。

转发警告 #1：我无法将列类型更改为 bit，因为这可能会破坏使用相同数据库的遗留 VB 应用程序我正在为其开发新应用程序.

前向警告 #2：我也不能使用 int 属性 ==> hidden bool 属性方法，因为在针对 Oracle 时需要使用完全相同的模型数据库（在 Oracle decimal(1,0) 中确实毫无问题地映射到 bool - 我需要在 SQL 服务器中实现同样的事情）。

假设我们有一个像这样的简单 table：

CREATE TABLE FOOBAR 
(
    FB_ID NUMERIC(11,0) PRIMARY KEY,
    FB_YN NUMERIC(1,0) NOT NULL
);

INSERT INTO FOOBAR (FB_ID, FB_YN)
VALUES (1, 1), (2, 0);

一个简单的 poco class:

public class FOOBAR 
{
     public long FB_ID {get; set;}

     // [Column(TypeName = "numeric(1,0)")]
     // ^--- doesn't work in ef6  =>  'The store type 'numeric(1,0)' could not be found in the SQL Server provider manifest'
     // ^--- allegedly this works in EF core with Microsoft.EntityFrameworkCore.Relational nuget package installed
     // ^--- https://docs.microsoft.com/en-us/ef/core/modeling/relational/data-types
     // ^--- but I couldn't find anything similar for EF 6
     public bool FB_YN {get; set;}
}

还有一个同样简单流畅的配置 class:

public class FOOBAR_FluentConfiguration : EntityTypeConfiguration<FOOBAR>
{
    public FOOBAR_FluentConfiguration()
    {
        ToTable(tableName: "FOOBAR");

        HasKey(x => x.FB_ID);

        // Property(x => x.FB_YN).HasColumnType("numeric(1,0)");
        // ^--- doesn't work in ef6  =>  'The store type 'numeric(1,0)' could not be found in the SQL Server provider manifest'
        // ^--- allegedly this works in EF core with Microsoft.EntityFrameworkCore.Relational nuget package installed
        // ^--- but I couldn't find anything similar for EF 6
    }
}

如评论中所述，任何试图说服 ef6 将 <bool> 映射到 table 中的 <numeric(1,0)> 列的尝试在运行时都惨遭失败。我也尝试通过 EF 约定达到预期的效果：

public sealed class MsSqlConventions : Convention
{
    public MsSqlConventions()
    {
        Properties<bool>().Configure(p => p.HasColumnType("numeric(1,0)")); //fails
    }
}

失败并显示以下消息：

The store type 'numeric(1,0)' could not be found in the SQL Server provider manifest

而这个：

public sealed class MsSqlConventions : Convention
{
    public MsSqlConventions()
    {
        Properties<bool>().Configure(p => p.HasColumnType("numeric").HasPrecision(1, 0)); //fails
    }
}

失败并显示以下消息：

Precision and scale have been configured for property 'FB_YN'. Precision and scale can only be configured for Decimal properties.

我还尝试玩弄（丰富）SQL 服务器提供商清单 a la:

DbProviderServices.GetProviderManifest();

但我还不能从中得出正面或反面。任何见解表示赞赏。

Answer 1

这是一种将 EF6 转为将数字 (1,0) 列作为 BIT 列处理的方法。这不是最好的东西，我只在底部显示的场景中测试过它，但就我的测试而言，它工作可靠。如果有人检测到事情没有按计划进行的极端情况，请随时发表评论，我会改进这种方法：

<!-- add this to your web.config / app.config -->
<entityFramework>
    [...]
    <interceptors>
        <interceptor type="[Namespace.Path.To].MsSqlServerHotFixerCommandInterceptor, [Dll hosting the class]">
        </interceptor>
    </interceptors>
</entityFramework>

以及拦截器的实现：

// to future maintainers     the reason we introduced this interceptor is that we couldnt find a way to persuade ef6 to map numeric(1,0) columns in sqlserver into bool columns
// to future maintainers     we want this sort of select statement
// to future maintainers     
// to future maintainers        SELECT 
// to future maintainers           ...
// to future maintainers           [Extent2].[FB_YN]  AS [FB_YN], 
// to future maintainers           ...
// to future maintainers        FROM  ...
// to future maintainers     
// to future maintainers     to be converted into this sort of select statement
// to future maintainers     
// to future maintainers        SELECT 
// to future maintainers           ...
// to future maintainers           CAST ([Extent2].[FB_YN]  AS BIT) AS [FB_YN],    -- the BIT cast ensures that the column will be mapped without trouble into bool properties
// to future maintainers           ...
// to future maintainers        FROM  ...
// to future maintainers
// to future maintainers     note0   the regex used assumes that all boolean columns end with the _yn postfix   if your boolean columns follow a different naming scheme you
// to future maintainers     note0   have to tweak the regular expression accordingly
// to future maintainers
// to future maintainers     note1   notice that special care has been taken to ensure that we only tweak the columns that preceed the FROM part  we dont want to affect anything
// to future maintainers     note1   after the FROM part if the projects involved ever get upgraded to employ efcore then you can do away with this approach by simply following
// to future maintainers     note1   the following small guide
// to future maintainers
// to future maintainers                                           https://docs.microsoft.com/en-us/ef/core/modeling/relational/data-types
// to future maintainers
public sealed class MsSqlServerHotFixerCommandInterceptor : IDbCommandInterceptor
{
    public void ScalarExecuting(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
    {
        HotfixFaultySqlCommands(command, interceptionContext);
    }

    public void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
    {
        HotfixFaultySqlCommands(command, interceptionContext);
    }

    public void NonQueryExecuting(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
    {
        HotfixFaultySqlCommands(command, interceptionContext);
    }

    public void ScalarExecuted(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
    {
    }

    public void ReaderExecuted(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
    {
    }

    public void NonQueryExecuted(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
    {
    }

    static private void HotfixFaultySqlCommands<TResult>(IDbCommand command, DbCommandInterceptionContext<TResult> interceptionContext)
    {
        if (!command.CommandText.TrimStart().StartsWith("SELECT", ignoreCase: true, culture: CultureInfo.InvariantCulture))
            return;

        command.CommandText = BooleanColumnSpotter.Replace(command.CommandText, "CAST ( AS BIT)");
    }

    static private readonly Regex BooleanColumnSpotter = new Regex(@"((?<!\s+FROM\s+.*)([[][a-zA-Z0-9_]+?[]][.])?[[][a-zA-Z0-9_]+[]])(?=\s+AS\s+[[][a-zA-Z0-9_]+?_YN[]])", RegexOptions.IgnoreCase);
}

还有一些快速测试：

{
  // -- DROP TABLE FOOBAR;
  // 
  // CREATE TABLE FOOBAR (
  // FB_ID NUMERIC(11,0) PRIMARY KEY,
  // FB_YN NUMERIC(1,0) NOT NULL,
  // FB2_YN NUMERIC(1,0) NULL
  // );
  // 
  // INSERT INTO FOOBAR (FB_ID, FB_YN, FB2_YN)
  // VALUES             (1, 0, 0);
  // 
  // INSERT INTO FOOBAR (FB_ID, FB_YN, FB2_YN)
  // VALUES             (2, 1, 1);
  // 
  // INSERT INTO FOOBAR (FB_ID, FB_YN, FB2_YN)
  // VALUES             (3, 1, null);

  var mainDatabaseContext = new YourContext(...);

  var test1 = mainDatabaseContext.Set<FOOBAR>().ToList();
  var test2 = mainDatabaseContext.Set<FOOBAR>().Take(1).ToList();
  var test3 = mainDatabaseContext.Set<FOOBAR>().Take(10).ToList();
  var test4 = mainDatabaseContext.Set<FOOBAR>().FirstOrDefault();
  var test5 = mainDatabaseContext.Set<FOOBAR>().OrderBy(x => x.FB_ID).ToList();
  var test6 = mainDatabaseContext.Set<FOOBAR>().Take(10).Except(mainDatabaseContext.Set<FOOBAR>().Take(10)).SingleOrDefault();
  var test7 = mainDatabaseContext.Set<FOOBAR>().Where(x => x.FB_ID == 1).ToList();
  var test8 = mainDatabaseContext.Set<FOOBAR>().Where(x => x.FB_YN).ToList();
  var test9 = (
      from x in mainDatabaseContext.Set<FOOBAR>()
      join y in mainDatabaseContext.Set<FOOBAR>() on x.FB_ID equals y.FB_ID into rightSide
      from r in rightSide.DefaultIfEmpty()
      select r
  ).ToList();

  var test10 = (
          from x in mainDatabaseContext.Set<FOOBAR>()
          join y in mainDatabaseContext.Set<FOOBAR>() on new {x.FB_YN, FB_YN2 = x.FB2_YN} equals new {y.FB_YN, FB_YN2 = y.FB2_YN} into rightSide
          from r in rightSide.DefaultIfEmpty()
          select r
      ).ToList();
}

Entity Framework 6 SQL 服务器上的代码优先：将 "bool" 映射到 "numeric(1,0)" 而不是 "bit"

Entity Framework 6 Code First on SQL Server: Map "bool" to "numeric(1,0)" instead of "bit"

c#

sql-server

entity-framework

entity-framework-6

ef-fluent-api