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SQL Server上的Entity Framework 6代码:将“bool”映射为“numeric(1,0)”,而不是“bit”

ef-fluent-api entity-framework-6 entity-framework sql-server c#

XDS · 技术社区 · 6 年前

前向警告0:升级到EF Core在不久的将来不是一个选项。

前向警告1:无法将列类型更改为 bit 因为这可能会破坏使用与我正在开发的新应用程序相同的数据库的传统vb应用程序。

提前警告2:我也不能使用 int property==>隐藏bool属性方法,因为在针对oracle数据库(在oracle中)时,需要使用相同的模型 decimal(1,0) 确实被映射到 bool 没有问题-我需要在sql server中实现同样的事情)。

假设我们有一个这样的简单表:

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类:

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;}
}

以及一个同样简单的fluent配置类:

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,试图说服EF6 <bool> 到 <numeric(1,0)> 表中的列在运行时失败得很惨。我也尝试过通过EF惯例来达到预期的效果:

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

此操作失败,并显示以下消息:

在SQL Server提供程序清单中找不到存储类型“numeric(1,0)”。

而这个:

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

此操作失败,并显示以下消息:

已为属性“fb-yn”配置精度和刻度。只能为十进制属性配置精度和小数位数。

我还尝试使用(enrich)sql server提供程序manifest a la:

DbProviderServices.GetProviderManifest();

但我还不能完全理解。任何见解都值得赞赏。

1 回复 | 直到 6 年前

XDS 6 年前

这里有一种方法可以将ef6武装起来,将数值(1,0)列作为位列处理。这不是最好的东西,我只在下面显示的场景中测试过它,但在我的测试中它是可靠的。如果有人发现一个角落的情况,事情没有按计划进行,请随意发表评论,我将改进此方法:

<!-- 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 ($1 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();
}