Solved

Help with error: Cannot implicitly convert type 'System.Collections.Generic.List<AnonymousType#1>' to 'System.Collections.Generic.List<string>'

Posted on 2013-12-13
21
3,953 Views
Last Modified: 2013-12-16
Im getting a slight problem, ive changed the original:

lst_CounterfeitParts = (from d in context.QA_CounterfeitParts select (d.PartNumber)).ToList();

Open in new window


changed to

lst_CounterfeitParts = (from d in context.QA_CounterfeitParts select (d.PartNumber, d.Manufacturer)).ToList();

Open in new window


I thought I solved the problem with

lst_CounterfeitParts = (from d in context.QA_CounterfeitParts select d.ToString()).ToList();

Open in new window


This returns no errors, but when I run the app it returns nothing?!

Thanks,
Dean
0
Comment
Question by:deanlee17
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 11
  • 10
21 Comments
 

Author Comment

by:deanlee17
ID: 39716914
Sorry I should have included this:

private List<String> lst_CounterfeitParts = new List<string>();

Open in new window

0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39717056
Your list is typed as a list<String> but the return type of your middle block is returning a list of an anonymous type with 2 params (part number and manufacturer).

Change the declaration to this:
private var lst_CounterfeitParts;

Open in new window

0
 

Author Comment

by:deanlee17
ID: 39717094
So replacing

private List<String> lst_CounterfeitParts = new List<string>(); 

Open in new window


with

private var lst_CounterfeitParts; 

Open in new window

0
Resolve Critical IT Incidents Fast

If your data, services or processes become compromised, your organization can suffer damage in just minutes and how fast you communicate during a major IT incident is everything. Learn how to immediately identify incidents & best practices to resolve them quickly and effectively.

 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39717109
Yes :)
0
 

Author Comment

by:deanlee17
ID: 39717125
The type or namespace name 'var' could not be found (are you missing a using directive or an assembly reference?)

The code site just after:

public partial class MainWindow : DXRibbonWindow
    {

Open in new window

0
 
LVL 11

Accepted Solution

by:
Angelp1ay earned 500 total points
ID: 39717193
Urgh sorry that's because it's defined as a field in the class not inside a method.

Ok... well instead let's just get explicit!

Create a private class:
        private class MyClass {
            public String PartNumber;
            public String Manufacturer;
        }

Open in new window


Declare your field member to be a list of that type:
List<MyClass> lst_CounterfeitParts = new List<MyClass>();

Open in new window


...and update your LINQ to this:
    this.lst_CounterfeitParts = (from d in context select new MyClass() { PartNumber = d.PartNumber, Manufacturer = d.Manufacturer }).ToList();

Open in new window

0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39717202
While we're talking about it, if you only need to enumerate then you could better define the member as an IEnumerable<MyClass>, and then you don't need to mess around with calling ToList(). I believe all LINQ methods operate on and return IEnumerables.
List<MyClass> lst_CounterfeitParts = new List<MyClass>();

...

lst_CounterfeitParts = (from d in context select new MyClass() { PartNumber = d.PartNumber, Manufacturer = d.Manufacturer });

Open in new window

0
 

Author Comment

by:deanlee17
ID: 39717218
haha ok now one error on:

Could not find an implementation of the query pattern for source type 'Ascent_ERP.AscentEntities'.  'Select' not found.
0
 

Author Comment

by:deanlee17
ID: 39717221
Sorry I hadn't seen your post above, will try that now.
0
 

Author Comment

by:deanlee17
ID: 39717234
Still get that error
0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39717413
Are you missing a reference?
using System.Linq;

Open in new window

0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39717471
...actually I think that would fail earlier.

Did you perhaps declare your field as just IEnumerable instead of IEnumerable<MyClass> ?
0
 

Author Comment

by:deanlee17
ID: 39718749
Sorry I missed this before I left work, I shall reply Monday morning.
0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39718751
If it still doesn't work can you post your code as complete as possible so I can check for any issues?
0
 

Author Comment

by:deanlee17
ID: 39720917
Ok I think ive missed the IEnumerable. So far I have the following:

List<MyClass> lst_CounterfeitParts = new List<MyClass>();

Open in new window


lst_CounterfeitParts = (from d in context select new MyClass() { PartNumber = d.PartNumber, Manufacturer = d.Manufacturer });

Open in new window


        private class MyClass
        {
            public String PartNumber;
            public String Manufacturer;
        } 

Open in new window



So should the top part be:

List IEnumerable <MyClass> lst_CounterfeitParts = new List<MyClass>();

Open in new window


Thanks for the help so far :)
0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39721015
The List<T> class implements the IEnumerable<T> interface, i.e. a list is an enumerable but an enumerable is not necessarily a list.

Top part should be:
IEnumerable<MyClass> lst_CounterfeitParts = new List<MyClass>();

Open in new window


LINQ methods tend to return generic IEnumerables instead of more specific Lists so if enumerables are sufficient for your needs it's less effort and more flexible to work entirely with them.
0
 

Author Comment

by:deanlee17
ID: 39721079
Could not find an implementation of the query pattern for source type 'Ascent_ERP.AscentEntities'.  'Select' not found.

on this line:

lst_CounterfeitParts = (from d in context select new MyClass() { PartNumber = d.PartNumber, Manufacturer = d.Manufacturer });

Open in new window


I thought maybe it could not find the table inside the entity framework so I changed it to

lst_CounterfeitParts = (from d in context.QA_CounterfeitParts select new MyClass() { PartNumber = d.PartNumber, Manufacturer = d.Manufacturer });

Open in new window


This seems to work in that the grid displays the correct number of rows, but the data in each cell is 'Ascent_ERP.MainWindow+MyClass'
0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39721125
Ok, that looks like progress!

I think the final step is that you're binding the entire MyClass to a field that is expecting a string. The data in the cell is the result of a call to ToString on the class itself (it's trying it's best to get the string).

I imagine in your grid markup you have some line that binds <? =Item ?> or something. Change this to Item.PartNumber or Item.Manufacturer as needed.
0
 

Author Comment

by:deanlee17
ID: 39721153
All done.

Thanks very much for all the help.

Just out of interest, the way we have done this using a class, is that common practise and a good template for me to use?
0
 
LVL 11

Expert Comment

by:Angelp1ay
ID: 39721305
Yea I think so.

It's quite explicit which means you can benefit from static analysis (e.g. when it won't compile it you catch bugs early!)

I typically use this pattern for converting (projecting) lists between 2 pre-existing types (List<InputType> --> List<OutputType>).
0
 

Author Comment

by:deanlee17
ID: 39721317
Thanks
0

Featured Post

Resolve Critical IT Incidents Fast

If your data, services or processes become compromised, your organization can suffer damage in just minutes and how fast you communicate during a major IT incident is everything. Learn how to immediately identify incidents & best practices to resolve them quickly and effectively.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

IP addresses can be stored in a database in any of several ways.  These ways may vary based on the volume of the data.  I was dealing with quite a large amount of data for user authentication purpose, and needed a way to minimize the storage.   …
More often than not, we developers are confronted with a need: a need to make some kind of magic happen via code. Whether it is for a client, for the boss, or for our own personal projects, the need must be satisfied. Most of the time, the Framework…
Are you ready to implement Active Directory best practices without reading 300+ pages? You're in luck. In this webinar hosted by Skyport Systems, you gain insight into Microsoft's latest comprehensive guide, with tips on the best and easiest way…

733 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question