Error: An expression tree may not contain a dynamic operation

Question

I use Asp.Net 4 and C#, I use EF 4.

I have this query, I receive an error:

 An expression tree may not contain a dynamic operation

dynamic o = e.Item.DataItem;
var imagesContent = context.CmsImagesContents.FirstOrDefault(img => img.ContentId == o.ContentId);

It seems is imposible to Cast a Dynamic Type using a Lamba Expression.

How I can fix the problem, and able to use my object o in my Lamba? Thanks

PS: e.Item.DataItem is of Type CmsContent and o.ContentId is of type Int

Can you cast `e.Item.DataItem` to the type that defines the `ContentId` property? — cdhowie, Aug 19 '11 at 07:58
I'm not able to do it inside the Lamba. Any idea how to make it? — GibboK, Aug 19 '11 at 08:00
`var o = (SomeType)e.Item.DataItem;` where `SomeType` is the type of object you are expecting. — cdhowie, Aug 19 '11 at 08:02
You need to show us why you *have to* declare `o` as `dynamic` first. — Cheng Chen, Aug 19 '11 at 08:04
duplicate of http://stackoverflow.com/questions/5614574/an-expression-tree-may-not-contain-a-dynamic-operation/14466282 -- better answer there — drzaus, Jan 22 '13 at 19:20

score 16 · Accepted Answer · edited Sep 24 '18 at 18:26

16

Unboxing the object will do the trick:

     int contentId = (int)o.ContentId;
     var image = context.CmsImagesContents.FirstOrDefault(img => img.ContentId == contentId);

For more info about 'boxing/unboxing' click here

edited Sep 24 '18 at 18:26

Jeric Cruz

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answered Aug 19 '11 at 08:13

GibboK

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score 4 · Answer 2 · answered Aug 19 '11 at 08:04

4

Change

dynamic o = e.Item.DataItem;

To

var o = (CmsContent)e.Item.DataItem;

answered Aug 19 '11 at 08:04

cdhowie

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score 0 · Answer 3 · answered Nov 22 '22 at 14:03

I was seeing this issue in code that was not using dynamics in any obvious way. I found it was caused by the inclusion of the below reference in the class using statements. Removing it seemed to change the way the the compiler interpreted the Linq expression.

using System.Linq.Dynamic.Core;

Error: An expression tree may not contain a dynamic operation

3 Answers3

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