LINQ Query help

Question

User-1825561198 posted

Hello :

I have a list

This Linq statement does not work. But that's the Idea

 DBDocuments.Where(x => DBDocumentAdditional .Find(a => a.DocumentId == x.DocumentId)).ToList().ForEach(t => t.Additional = DBDocumentAdditional );

Model:

public class Document
{
        public long DocumentId { get; set; }
        public List<DocumentAdditional> Additional { get; set; }
}

 public class DocumentAdditional
    {
        public long DocumentId { get; set; }
        public string Name { get; set; }
        public string Value { get; set; } 
    }

List<Document> DBDocuments = new List<Document>();

List<DocumentAdditional> DBDocumentAdditional = new List<DocumentAdditional>();

I populate DBDocuments  list with some data from database.This List has a key which is DocumentId.

I populate DBDocumentAdditional list with some data from database.This List has a key which is DocumentId.

Now I want to use LINQ to add the DBDocumentAdditional list  to the DBDocuments  list, for the Matching DocumentId's. List within a List with Matching Id

I am kind of stuck on syntax to do this. Please suggest, or help.

Thank you,

Answer 1

User281315223 posted

This is because DocuementId is a long and you are attempting to compare it to a string (e.g. "123"). You would likely want to convert or parse this value into a long and then use that as your parameter :

// Convert your value a 64-bit integer (long)
var id = Convert.ToInt64("123");
DBDocuments.Where(x => x.DocumentId == id ).ToList().ForEach(t => t.AdditionalAttributes = DBAdditionalAttribute);

Answer 2

User-1825561198 posted

Thank you for the Reply. Idea is Don't want to Hard code the id. 

id is saved in DBDocuments and DBDocumentAdditional.

It's kind of like this

 DBDocuments.Where(x => DBDocumentAdditional .Find(a => a.DocumentId == x.DocumentId)).ToList().ForEach(t => t.Additional = DBDocumentAdditional );

Answer 3

User-2057865890 posted

Hi urpalshu,

I have achieved your needs on my side. You could solve your problem with the suggestion what I gave in the below.

//Get all the ID set
List<long> idlist = DBDocuments.Select(c => c.DocumentId).ToList();
  
//Get the value by ID
var query = DBDocumentAdditional.Where(c => idlist.Contains(c.DocumentId)).GroupBy(c => c.DocumentId).Select(c => new { ID = c.Key, list = c.ToList() });
  
foreach( var item in query)
{
   //assign
   List<DocumentAdditional> li = item.list;
   Document dtm = DBDocuments.Where(c => c.DocumentId == item.ID).FirstOrDefault();
   dtm.Additional = li;
   //displaying
   Response.Write(item.ID);
   Response.Write("<br />");
   foreach(var additem in li)
   {
       Response.Write(additem.Name);
       Response.Write("<br />");
       Response.Write(additem.Value);
       Response.Write("<br />");
    }
}

Best Regards,

Chris Zhao

Answer 4

User281315223 posted

You could perform the conversion within your lambda statements if I understand you correctly :

DBDocuments.Where(x => DBDocumentAdditional.Find(a => a.DocumentId == Convert.ToInt64(x.DocumentId)))
           .ToList()
           .ForEach(t => t.Additional = DBDocumentAdditional );

You may have throw an AsEnumerable() or a ToList() call prior to your Find method to ensure that LINQ knows how to resolve that.