CODEWITHSUNDEEP
c#linq
Michael Esteves
Michael Esteves

Reputation: 1485

Declare variable within LINQ select(x => new

I'm mapping a POCO into a model, code shown below.

// NOT NEEDED var noneRequiredUserDocuments = new List<NoneRequiredUserDocument>();
//var docs = studentDocuments.Where(x => x.RequiredUserDocumentId == null); // NOT NEEDED .ToList();
//var noneRequiredUserDocuments = docs.Select(x => new NoneRequiredUserDocument

// You can chain LINQ methods (i.e. Where and Select)
var noneRequiredUserDocuments = studentDocuments
    .Where(x => x.RequiredUserDocumentId == null)
    .Select(x => new NoneRequiredUserDocument
    {
        StudentDocument = x,
        Src = _storageService.GetFileUrl(x.FileName),
        ThumbnailImageUrl = ImageHelper.ThumbnailImageUrl(Src, 75)

    }).ToList();

My problem is that in this line:

ThumbnailImageUrl = ImageHelper.ThumbnailImageUrl(Src, 75)

Src doesn't exist in the context.

Is there a way for me to declare a variable within the select that I can the reuse within the LINQ select?

And I don't want to call _storageService.GetFileUrl twice.

Upvotes: 47

Views: 62218

Answers (4)

Veverke
Veverke

Reputation: 11348

you can create a regular code block instead of running a single statement within the lambda expression, this way you can just declare a variable "src" and it will be available throughout the entire block - following regular scope rules.

noneRequiredUserDocuments = docs.Select(x => {
      var  src = _storageService.GetFileUrl(x.FileName);
      return 
             new NoneRequiredUserDocument
             {
                 StudentDocument = x,
                 Src = src,
                 ThumbnailImageUrl = ImageHelper.ThumbnailImageUrl(Src, 75)
              };
    }).ToList();

Upvotes: 10

Rahul Singh
Rahul Singh

Reputation: 21795

You can declare a variable inside a Select like this:-

noneRequiredUserDocuments = docs.Select(x => 
  {
      var src= _storageService.GetFileUrl(x.FileName);
      return new NoneRequiredUserDocument
     {
        StudentDocument = x,
        Src = src,
        ThumbnailImageUrl = ImageHelper.ThumbnailImageUrl(src, 75);
     };
  }).ToList();

In query syntax doing this is equivalent to:-

from x in docs
let src= _storageService.GetFileUrl(x.FileName)
select and so on..

Upvotes: 88

Tsef
Tsef

Reputation: 1038

You can use the "let" keyword:

var list = (from x in docs
            let temp = _storageService.GetFileUrl(x.FileName)
            select new NoneRequiredUserDocument
            {
                StudentDocument = x,
                Src = temp,
                ThumbnailImageUrl = ImageHelper.ThumbnailImageUrl(temp, 75)
            }).ToList();

Upvotes: 16

Konrad Kokosa
Konrad Kokosa

Reputation: 16878

You can introduce temporary collection of anonymous type, with all necessary data:

noneRequiredUserDocuments = docs
   .Select(x => new { Data = x, Src = _storageService.GetFileUrl(x.FileName) }
   .Select(x => new NoneRequiredUserDocument
   {
       StudentDocument = x.Data,
       Src = x.Src
       ThumbnailImageUrl = ImageHelper.ThumbnailImageUrl(x.Src, 75)
   }).ToList();

Upvotes: 3

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