对象的EF6关系映射

Question

问题（或低智商）

我正在尝试为报表数据库的复杂对象创建EF6映射配置。重新思考对象的结构可能是一个更明智的事情。但关键因素是我正在从生成的XSD方案中创建这个，我想保持这两个东西的一致性。

这是对象的定义:(非常简化！）

报告是“基类”

class Report  
{
    public HeaderObj headerobj {get;set;}
    public DataObj dataObj {get;set;}
}

class HeaderObj 
{
    public DateTime date {get; set;}
    public string fundID {get;set;}
}

class DataObj
{
    public ICollection<Investment> investments {get;set;}
}

class Investment
{
    //....lot of member objects here like Amount and other things..you get the drill.
}

这是我对映射conf的实验：

public class ReportMapping: EntityTypeConfiguration<Report>
{
    public ReportMapping()
        {
//has a composite key: date and fundid, in the object HeaderObj, probably be better off directly under Report class but as im saying, I'm trying to have consistency between the c# classes and the orginal XSD schema.

HasKey(a => new {a.headerobj.date, a.headerobj.fundID});

HasRequired(a => a.HeaderObj);

HasRequired(a => a.dataObj).WithMany(s => s.investments); <-- "computer say no here" although this does make sense to me 

        }
}

// ...

Cannot implicitly convert type 'System.Collections.Generic.ICollection<Investment>' to 'System.Collections.Generic.ICollection<Report>'. An explicit conversion exists (are you missing a cast?)

如何在没有编译错误的情况下为对象DataObj定义多个投资的正确映射？