C# Add Object To List

Question

I have created a new empty List of type User (User is an Entity in my EDM)

List<User> AvailableLocums = new List<User>();
AvailableLocums = null;

I also have another List of type User which is populated with the results of a query

List<User> Locums = _shiftDateService.GetAvailableLocums(id, shiftDate.shiftDateID).ToList();

I then wish to loop around the Locums List, do some logic, and then add the User to my AvailableLocums List

foreach (var locum in Locums)
{
   //Do some logic

   AvailableLocums.Add(locum);

}

However, when I try to do this I get the following error

Object reference not set to an instance of an object.

I then tried to amend my code and do the following

foreach (var locum in Locums)
{
       //Do some logic

       User locumUser = new User();
       locumUser = locum;

       AvailableLocums.Add(locumUser);     
}

But again I get the same error

Object reference not set to an instance of an object.

Could someone please help me with this?

Thanks.

Fredrik · Accepted Answer · 2012-09-18 11:20:45Z

5

You are telling your variable "AvailableLocums" to no longer point to anything in memory.

Remove: AvailableLocums = null;

how about:

List<User> AvailableLocums;
List<User> Locums;

// get id for shift date service
// int id = ...

// get locums from shift date service 
Locums = _shiftDateService.GetAvailableLocums(id, shiftDate.shiftDateID).ToList();

// time to add to AvailableLocums
if(AvailableLocums == null)
    AvailableLocums = new List<User>();

foreach (var locum in Locums)
{
   //Do some logic

   AvailableLocums.Add(locum);
}

edited Sep 18, 2012 at 11:20

answered Sep 18, 2012 at 11:01

Fredrik

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Comments

Daniel A. White · Accepted Answer · 2012-09-18 10:57:16Z

3

You are nulling out that list

List<User> AvailableLocums = new List<User>();
AvailableLocums = null; // HERE

hence, the exception. You don't need this line to make an empty list:

AvailableLocums = null;

answered Sep 18, 2012 at 10:57

Daniel A. White

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Comments

Davecz · Accepted Answer · 2012-09-18 10:58:17Z

1

get out this line :

AvailableLocums = null;

and it will be Ok ... You declaring new object and on next row set it to null?

answered Sep 18, 2012 at 10:58

Davecz

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Comments

maxs87 · Accepted Answer · 2012-09-18 10:59:46Z

0

try to

List<User> Locums = new List<User>();

before _shiftDateService.GetAvailableLocums...

answered Sep 18, 2012 at 10:59

maxs87

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Comments

Vijay Sawariya · Accepted Answer · 2012-09-18 11:46:13Z

0

Try this code.

List<User> AvailableLocums = null; 
List<User> Locums = _shiftDateService.GetAvailableLocums(id, shiftDate.shiftDateID).ToList();  
AvailableLocums = Locums.Where(newUserRecord => newUserRecord != null).ToList();

* you can take any name instead of "newUserRecord".

answered Sep 18, 2012 at 11:46

Vijay Sawariya

1

1 Comment

Vijay Sawariya Over a year ago

you can use Lambda expression instead of using foreach

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