concatenate strings in LINQ query - entity-framework

Question

Suppose I want to set FullName property using string.Format like this:
var userList = users.Select(user => new User()
{
Id = user.Id,
UserName = user.UserName,
FirstName = user.FirstName,
LastName = user.LastName
FullName = string.Format("{0} {1}", user.UserName, user.FirstName)
}).ToList();
This obviously doesn't work because LINQ doesn't know about string.Format.
My question is what are the other options beside going over the list in memory and setting FullName for each item?
userList.ForEach(u => u.FullName = string.Format("{0} {1}", user.UserName, user.FirstName))
UPDATE: to see what I need, please see my conversation with #octavioccl below

Answer 1

you can use it:
FullName = user.UserName + " " + user.FirstName
But I think that it could be better solution (of cource if it's possible for you):
public class User
{
public int Id {get;set;}
public string UserName {get;set;}
public string FirstName {get;set;}
public string LastName {get;set;}
public string FullName
{
get
{
return string.Format("{0} {1}", FirstName, LastName);
}
}
}
then in your query build it:
var userList = users.Select(user => new User()
{
Id = user.Id,
UserName = user.UserName,
FirstName = user.FirstName,
LastName = user.LastName
}).ToList();

Answer 2

String.Format is not supported in EF, try this way:
FullName = user.UserName + " " + user.FirstName
In this link you will find all CLR methods that are supported

Answer 3

Another object is to project to an anonymous type without that property, then project to the final type in linq-to-objects:
var userList = users.Select(user => new {
Id = user.Id,
UserName = user.UserName,
FirstName = user.FirstName,
LastName = user.LastName
})
.AsEnumerable()
.Select(user => new User()
{
Id = user.Id,
UserName = user.UserName,
FirstName = user.FirstName,
LastName = user.LastName
FullName = string.Format("{0} {1}", user.UserName, user.FirstName)
})
.ToList();