create Lambda Expression with reflection in c#

Question

I need to Create the following Lambda Expression :

{d=>d.Name.NameEn}

I wrote the following code:

ParameterExpression parameter = Expression.Parameter(typeof(T), "d");
MemberExpression memberExpression = Expression.Property(parameter, typeof(T).GetProperty("Name"));
LambdaExpression lambda = Expression.Lambda(memberExpression, parameter);

Output :

{d => d.Name}

But I need this :

{d=>d.Name.NameEn}

How to make this ?

update:

my class :

 public class T
    {
        public U Name { get; set; }
    }
    public class U
    {
        public string NameEn { get; set; }
    }

Joey · Accepted Answer · 2016-02-18 06:29:22Z

1

In that case you need to wrap the expression in another MemberExpression, e.g.:

var outerMemberExpression = Expression.Property(memberExpression, typeof(U).GetProperty("NameEn"));

and use that for your lambda expression. You do have two member access expressions there, after all: One to access Name, and one to access NameEn.

answered Feb 18, 2016 at 6:29

Joey

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Jcl · Accepted Answer · 2016-02-18 06:29:29Z

0

You can try:

ParameterExpression parameter = Expression.Parameter(typeof(T), "d");
MemberExpression memberExpression = 
    Expression.Property(parameter, typeof(T).GetProperty("Name"));
MemberExpression memberExpressionInner = 
    Expression.Property(memberExpression,
                        typeof(T).GetProperty("Name").PropertyType.GetProperty("NameEn"));
LambdaExpression lambda = Expression.Lambda(memberExpressionInner, parameter);

Or, if U is known at runtime (I was assumming T would be a generic parameter before your update), the third line could be:

MemberExpression memberExpressionInner = 
    Expression.Property(memberExpression, typeof(U).GetProperty("NameEn"));

answered Feb 18, 2016 at 6:29

Jcl

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