Changing EF6 source code for conversion of short to bool

问题

What is the feasibility of modifying the mapping code to convert a short of value zero or non-zero to false or true, if the boolean destination property is marked with an attribute in the POCO model?

I mean, this is supposed to be one of the advantages of EF being open sourced, and would be for in house use only.

Any tips on where in the code I would look would be appreciated, but this question is really more general and I'd like to hear anything anyone has to say on this.

回答1:

With regard to the General comments please. I dont know to make the EF change, but dealing with similar issues is not an uncommon issue in EF. Not all standard types are supported by EF.

You can have a helper field in your POCO class. So one field is the actual DB field, but no used outside of POCO. The help field is NOTMAPPED or ignored in fluent API. You access the DB via you helper and execute any required casting. A simple example. Or the reverse if I got helper and DB field types back to front.

   [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); }  }

Edit: Power Fluent API Here is a snippet that outlines how you have code that runs for every mapped poco in a consistent way.

 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;
    }

来源：https://stackoverflow.com/questions/19929292/changing-ef6-source-code-for-conversion-of-short-to-bool