c# - 通过继承改变返回签名——多态

Question

只是想知道是否有任何方法可以执行以下操作:

public Interface IDataField 
{
    object GetValue();
}

public Interface IComplexDataField : IDataField
{
    object GetDefaultValue();
}

public class MyBase
{
    private IDataField _DataField;

    public MyBase()
    {
        this._DataField = this.CreateDataField();
    }

    public virtual IDataField CreateDataField()
    {
        return new DataField(); //Implements IDataField 
    }

    **public virtual IDataField GetDataField()**
    {
        return this._DataField;
    }

    public void SomeMethod()
    {
        this.GetDataField().GetValue();
    }
}


public class MyComplexBase : MyBase
{
    public override IDataField CreateDataField()
    {
        return new ComplexDataField(); //Implements IComplexDataField which Implements IDataField 
    }

    **public override IComplexDataField GetDataField()**
    {
        return (IComplexDataField)base.GetDataField();
    }

    public void SomeComplexSpecificMethod()
    {
        this.GetDataField().GetValue();
        this.GetDataField().GetDefaultValue();
    }
}

干杯 安东尼

Answer 1

您想要的是返回类型的协方差。这在 C# 中不存在。

你能否使 MyBase 通用:

public class MyBase<T> where T : IDataField
{
    public virtual T CreateDataField()
    {
        ... etc ...
    }
}

或者，您可以使用“new”重新声明该方法并隐藏基类方法。两者都不是特别吸引人......