相关隐约到$p$pvious问题 的

注意：我使用的是防爆pressionTree游客的衍生物作为解释的这里 的

Note : I'm using a derivative of the ExpressionTree visitor as explained here

在我的 VisitMemberAccess 方法，我现在创建使用的线沿线的东西MemberEx pressions：

In my VisitMemberAccess method I currently create MemberExpressions using something along the lines of:

// `mapping` is a class used to map EntityA's members to EntityB's members
return Expression.MakeMemberAccess(Visit(m.Expression), mapping.TargetMemberInfo);

在大多数情况下，这个工程。

For the most part, this works.

由于一些测试类...

Given some test classes...

public class EntityA
{
    public long Id { get; set; }
    public string Name { get; set; }
}

public class EntityB
{
    public long MyId {get; set; }
    public string MyName { get; set; }
}

在code将正确映射（EntityA X）=＆GT; x.Id 到（EntityB X）=＆GT; x.MyId 这是伟大的，工作可爱。当你引入导航属性我的问题就来了：

The code will correctly map (EntityA x) => x.Id to (EntityB x) => x.MyId which is great and works lovely. My problem comes when you introduce navigation properties:

public class EntityB
{
    public long MyId {get; set; }
    public EntityBDetails NavigationProperty { get; set; }
}    

public class EntityBDetails
{
    public string MyName { get; set; }
}

鉴于上述简单的情况，我想（EntityA x）x =＆GT; x.Name 映射到（EntityB x）x =＆GT; x.NavigationProperty.Name 。而therelies的问题，我不知道该怎么提供给 MakeMemberAccess 来使这项工作......我可以比较 mapping.TargetMemberInfo.DeclaringType == mapping.TargetMemberInfo.ReflectedType 来确定是否有涉及导航属性，但我如何创建必要的MemberEx pression？

Given the above trivial case, I would want (EntityA x) x => x.Name to map to (EntityB x) x => x.NavigationProperty.Name. And therelies the problem, I have no idea what to supply to MakeMemberAccess to make this work... I can compare mapping.TargetMemberInfo.DeclaringType == mapping.TargetMemberInfo.ReflectedType to determine whether there is a navigation property involved, but how do I create the necessary MemberExpression?

在此先感谢！

注：在code碱基我的工作是VB; C＃中往往获得更好/更快速的答案在SO所以我一直用手工转换。让我知道如果我做了愚蠢的拼写错误的/ etc 的

推荐答案

我觉得它可以帮助翻译C＃code成英文，然后它转换成一个前pression创造code

I think it could help to translate the C# code into English, and then translate that into an expression-creating code:

这位前pression x.NavigationProperty.Name 其实就是访问属性 NavigationProperty 在 X ，然后访问属性名称的结果。现在，code：

The expression x.NavigationProperty.Name actually means "access property NavigationProperty on x and then access property Name on the result. Now, the code:

ParameterExpression x = …;
var navigationProperty = typeof(EntityB).GetProperty("NavigationProperty");
var name = typeof(EntityBDetails).GetProperty("Name");

var navigationPropertyAccess = Expression.MakeMemberAccess(x, navigationProperty);
var nameAccess = Expression.MakeMemberAccess(navigationPropertyAccess , name);