How to get rid of the error 'System.Collections.Generic.IEnumerable' does not contain a definition for 'ToList'

Niladri.biswas
Posted by Niladri.biswas under Error and Solution category on | Points: 40 | Views : 16482
Suppose we have the below entities

class PersonName
{
public int Id { get; set; }
public string Name { get; set; }
}

class PersonAddress
{
public int Id { get; set; }
public string Address { get; set; }
}

class PersonInfo
{
public int Id { get; set; }
public string Name { get; set; }
public string Address { get; set; }
}


Now we want to combine the result of the PersonName and PersonAddress collection and the combined result want to store in List PersonInfo.

Intially the program was

List<PersonName> lstPersonName = new List<PersonName>();
Enumerable.Range(1, 10).ToList().ForEach(i => lstPersonName.Add(new PersonName { Id = i, Name = "Name" + i.ToString() }));

List<PersonAddress> lstPersonAddress = new List<PersonAddress>();
Enumerable.Range(1, 10).ToList().ForEach(i => lstPersonAddress.Add(new PersonAddress { Id = i, Address = "Address" + i.ToString() }));

List<PersonInfo> lstPersonInfo =
(
from a in lstPersonName
join b in lstPersonAddress on a.Id equals b.Id
select new
{
Prop1 = a.Id
,
Prop2 = a.Name
,
Prop3 = b.Address
}
).ToList();


Upon compiling, we encounter the below error

'System.Collections.Generic.IEnumerable<AnonymousType#1>' does not contain a definition for 'ToList' and the best extension method overload 'System.Linq.Enumerable.ToList<TSource>(System.Collections.Generic.IEnumerable<TSource>)' has some invalid arguments

Then we changed the .ToList() to .ToList<PersonInfo>() as under

List<PersonInfo> lstPersonInfo =
(
from a in lstPersonName
join b in lstPersonAddress on a.Id equals b.Id
select new
{
Prop1 = a.Id
,
Prop2 = a.Name
,
Prop3 = b.Address
}
).ToListList<PersonInfo>();

but with the same error.

Now why it is happening?

Because, we tried to create a sequence of a new anonymous type and tried to call ToList<PersonInfo> on it which will never work. We should create a PersonInfo
directly by writing new PersonInfo { ... } as under

List<PersonInfo> lstPersonInfo =
(
from a in lstPersonName
join b in lstPersonAddress on a.Id equals b.Id
select new PersonInfo
{
Id = a.Id
,
Name = a.Name
,
Address = b.Address
}
).ToList();


Hope this is useful.

Comments or Responses

Posted by: Hmanjarawala on: 12/14/2011 Level:Bronze | Status: [Member] | Points: 10
Hi niladri,
this is simple example for illustration.

thanks for this

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