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如果布尔目标属性在 POCO 模型中标记有属性，那么修改映射代码以将short值为零或非零的 a 转换为 false 或 true 的可行性是什么？

我的意思是，这应该是 EF 开源的优势之一，并且仅供内部使用。

任何关于我在代码中的位置的提示将不胜感激，但这个问题确实更笼统，我想听听任何人对此的看法。

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1 回答 1

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关于一般性意见，请。我不知道要更改 EF，但处理类似问题在 EF 中并不少见。并非所有标准类型都受 EF 支持。

您可以在 POCO 类中有一个辅助字段。所以一个字段是实际的 DB 字段，但在 POCO 之外没有使用。在 fluent API 中，帮助字段是 NOTMAPPED 或忽略的。您可以通过您的助手访问数据库并执行任何所需的转换。一个简单的例子。或者如果我将助手和数据库字段类型重新放在前面，则相反。

   [NotMapped]
    public virtual bool IsVisible { set; get; }  // Helper Field NOT on DB
    public int Test { get { return IsVisible ? 1 : 0; } //  on DB, but set and get via helper only.
                      set { IsVisible = (value != 0); }  }

编辑：Power Fluent API 这是一个片段，概述了如何以一致的方式为每个映射的 poco 运行代码。

 public class MyDbContext : DbContext 
// model building, set breakpoint so you know when this is triggered   
// it is important this ISNT called everytime, only on model cache.
// in my case that is app pool recycle.

protected override void OnModelCreating(DbModelBuilder modelBuilder)
    // use the CONFIG add feature to better organize and allow use of inheritance when mapping
    // I will use snippets and statics to keep it simple. 
        modelBuilder.Configurations.Add(XYZMap.Map()); //  POCO map 
        modelBuilder.Configurations.Add(ABCMAP.Map()); //  poco map
        modelBuilder.Configurations.Add(XXXMap.MAP()); //  poco map
    // etc for your POCO set
    // Note, no need to declare DBset<xyz> XYZs {get;set;} !!!!

     public static class XYZMap {
    public static BaseEntityIntConfiguration<PocoXYZ> Map() {
        //see return object !
        var entity = new BaseEntityLongConfiguration<PocoXYZ>();
         //entity.Property()...   // map away as usual POCO specifc
        ///entity.HasRequired()...// property and relationships as required
                                  // do nothing for default
        return entity;
       }
    }
}


 // all tables with int key use this base config. do it once never again
 public class BaseEntityIntConfiguration<T> : BaseEntityConfiguration<T> where T : BaseObjectInt {
    public BaseEntityIntConfiguration(DatabaseGeneratedOption DGO = DatabaseGeneratedOption.Identity) {
        // Primary Key
        this.HasKey(t => t.Id);

        // Properties
        //Id is an int allocated by DB
        this.Property(t => t.Id).HasDatabaseGeneratedOption(DGO); // default to db generated
        // optimistic lock is also added here, Specific to out poco design
        this.Property(t => t.RowVersion)
            .IsRequired()
            .IsFixedLength()
            .HasMaxLength(8)
            .IsRowVersion();

        // any other common mappings/ rules ?? 

    }
}

   public class BaseEntityConfiguration<T> : EntityTypeConfiguration<T> where T : BaseObject {
    public BaseEntityConfiguration() {
            this.ApplyAttributeRules();   // <<<<< Here is where I apply SYSTEM WIDE rules
    }
}


  public static void ApplyAttributeRules<T>(this EntityTypeConfiguration<T> entity) where T : BaseObject {
  // so this will be called for each mapped type

   foreach (var propertyInfo in typeof (T).GetProperties()) {
       // I use reflection to look for properties that meet certain criteria.
       // eg string.  I want as NVARCHAR 4000 not NVCAHR max so i can index it.
      if (propertyInfo.UnderLyingType().FullName == "System.String") {
                    SetStringLength(BosTypeTool.StringLengthIndexable, propertyInfo.Name, entity);
                    continue;
                }  

        SetStringLength(4000, propertyInfo.Name, entity); 

   }

 }
  private static void SetStringLength<TModelPoco>(int length, string propertyName,
        EntityTypeConfiguration<TModelPoco> entity) where TModelPoco : BaseObject {
        var propLambda = DynamicExpression.ParseLambda<TModelPoco, String>(propertyName);
        entity.Property(propLambda).HasMaxLength(length);
  // dynamic library from Microsoft.... http://msdn.microsoft.com/en-US/vstudio/bb894665.aspx
    }
 // get underlying type incase it is nullable
 public static Type UnderLyingType(this PropertyInfo propertyInfo) {
        return Nullable.GetUnderlyingType(propertyInfo.PropertyType) ??                  propertyInfo.PropertyType;
    }
于 2013-11-17T12:56:18.543 回答