CODEWITHSUNDEEP
c#linq
jimjim
jimjim

Reputation: 2503

using methods within Linq projection

Given the following code :

        var EmployeeXPosition = from emp in context.WTDEmployee
                                from ep in emp.WTDEmployeeXOXPosition
                                select new { 
                                    EmployeeId = emp.id, 
                                    FullNameAndPosition =  string.Format("{0} {1} : {2}", emp.FirstName, emp.LastName, ep.WTDPosition.Position) 
                                };

It gives the error :

LINQ to Entities does not recognize the method 'System.String Format(System.String, System.Object, System.Object, System.Object)' method, and this method cannot be translated into a store expression.

Sure enough I could do :

 emp.FirstName+" "+ emp.LastName +" : " + ep.WTDPosition.Position

But it just looks ugly, any suggestions on how to use string.Format instead ?

Upvotes: 4

Views: 1450

Answers (2)

Simon_Weaver
Simon_Weaver

Reputation: 146160

This codeplex project claims to do exactly what you want. Unfortunately I don't have time to try it now - but here's what they say

LINQ Expression Projection library provides tool that enable using lambda expressions in LINQ projections (to anonymous and predefined types) even if the lambda expression is not defined in the query but rather is stored in a variable or retrieved via a function or property.

Upvotes: 1

Slaggg
Slaggg

Reputation: 6471

I usually solve this by creating two statements - one in LinqToEntities (or ToSql, or whatever) and then another in LinqToObjects. I do what I need to do in the store, and then do a separate processing step with the objects in memory. This mixes the best of both worlds.

 var EmployeeXPosition = from emp in context.WTDEmployee
                                from ep in emp.WTDEmployeeXOXPosition
                                select new { 
                                    emp.id, 
                                    emp.FirstName, 
                                    emp.LastName,
                                    ep.WTDPosition.Position
                                };

var result = from item in EmployeeXPosition.ToList()
             select new 
             {
                EmployeeId = item.id, 
                FullNameAndPosition =  string.Format("{0} {1} : {2}", item.FirstName, item.LastName, item.Position) 
             };

Upvotes: 5

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