CODEWITHSUNDEEP
c#linqdynamicsystem.linq.dynamic
dagon
dagon

Reputation: 67

Linq.Dynamic FirstOrDefault() nested in OrderBy

I have the following Linq statement, which works totally fine:

query = query.OrderBy(m => m.MATERIAL_TXT.Where(mt => mt.LANG == "EN").FirstOrDefault().LTEXT);

Now I'm trying to make it dynamic by using the string based syntax from Linq.Dynamic:

query = query.OrderBy("MATERIAL_TXT.Where(LANG==\"EN\").FirstOrDefault().LTEXT");

But it throws the exception :

"No applicable aggregate method 'FirstOrDefault' exists"

It has to bedynamic so that it accepts other names instead of "MATERIAL_TXT".

What am I missing?

Upvotes: 3

Views: 1106

Answers (2)

masoud
masoud

Reputation: 375

You can't use FirstOrDefault as string like that.

if you want to create dynamic orderBy try this :

Func<IQueryable<YourEntityType>, IOrderedQueryable<YourEntityType>> orderBy;

   orderBy = x => x.OrderBy(m => m.MATERIAL_TXT.Where(mt => mt.LANG == "EN").FirstOrDefault().LTEXT);

Then you can use it like this :

orderBy(query);

for example you can use it in another method :

public List<YourEntityType> YourMethodName(Func<IQueryable<YourEntityType>, IOrderedQueryable<YourEntityType>> orderBy,IQueryable<YourEntityType> query=null)
{
     query=query ?? GetYourEntityTypeList().AsQueryable();
     return orderBy(query).ToList();
}

I Hope it will be useful .

Upvotes: 1

Luaan
Luaan

Reputation: 63722

According to the documentation:

A subset of the Standard Query Operators is supported for objects that implement IEnumerable. Specifically, the following constructs are permitted, where seq is an IEnumerable instance, predicate is a boolean expression, and selector is an expression of any type:

  • seq.Where(predicate)
  • seq.Any()
  • seq.Any(predicate)
  • seq.All(predicate)
  • seq.Count()
  • seq.Count(predicate)
  • seq.Min(selector)
  • seq.Max(selector)
  • seq.Sum(selector)
  • seq.Average(selector)

FirstOrDefault isn't on the list, so it's reasonably safe to assume it isn't supported.

Upvotes: 1

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