"Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type" during Index Creation

[Shubha Lakshmi]

I am trying to create a simple index, something  like this :

 

public class Services_ByAll : AbstractIndexCreationTask<Service, Services_ByAll.Result>
    {
       
        public class Result
        {

             public string MyFieldOne{get;set;}
             public string MyFieldTwo{get;set;}
             public string MyFieldThree{get;set;}
             public string MyFieldFour{get;set;}

        }

        public Services_ByAll()
        {
            Map = (services) => from service in services
                                let arg1 = service.MyFieldOne.Split('-').Aggregate((i, j) => i + " " + j)
                                let arg2 = service.MyFieldThree.Split('-').Aggregate((i, j) => i + " " + j)
                               
                                select new Result
                                {
                                   
                                     MyFiledOne = service.MyFieldOne,
                                     MyFieldThree =service.MyFieldThree,
                                     MyFieldTwo = arg1,
                                     MyFieldFour = arg2

                                };
            //Make text fields as Analyzed, in order to enable full text search on them


            Indexes.Add(entry => entry.MyFieldTwo, FieldIndexing.Analyzed);
            Indexes.Add(entry => entry.MyFieldFour, FieldIndexing.Analyzed);
           


            Analyzers.Add(x => x.MyFieldTwo, typeof(StandardAnalyzer).AssemblyQualifiedName);
            Analyzers.Add(x => x.MyFieldFour, typeof(StandardAnalyzer).AssemblyQualifiedName);    


        }
   }

However, When I am running the application, I am getting a run time exception that "Error CS1977 - Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type".

Any pointers would help.

TIA

[Mrinal Kamboj]

Can you paste the code which is using this index internally, thus leading to exception. There's a possibility of not creating the Expression tree correctly.

[Shubha Lakshmi]

Not Sure, because it is run-time generated error.

Posting partial Stack Trace here :

15:19:14, Error, InnerExceptionMessage :: 1 :: Failed to compile index name = Services/ByAll :: ,
15:19:14, Error, InnerExceptionSource :: 1 :: :: ,
15:19:14, Error, InnerExceptionStackTrace :: 1 :: :: ,
15:19:14, Error, InnerExceptionMessage :: 2 :: Compilation Errors: Line 75, Position 9: Error CS1977 - Cannot use a lambda expression as an argument to a dynamically dispatched operation without first casting it to a delegate or expression tree type

[Oren Eini (Ayende Rahien)]

Use:

                                let arg1 = service.MyFieldOne.Replace('-', ' ').

Or:

                                let arg1 = string.Join(" " , service.MyFieldOne.Split('-'))

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Office: +972-4-622-7811 l Fax: +972-153-4-622-7811

 

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[Shubha Lakshmi]

Thanks Oren , that worked! But I am not able to understand what is the difference between 

service.MyFieldOne.Split('-').Aggregate((i, j) => i + " " + j)

and 

 service.MyFieldOne.Replace('-',' ')

I mean what caused the exception to go away ...

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[Oren Eini (Ayende Rahien)]

The issue is that Aggregate isn't recognized on the server side, which cause the issue

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