I've just started using AutoMapper to map Database with Model. I've two tables and I've applied join between them. Also, I have created class which combines both the classes. Now I want to Auto Map this join result to variable.
var demo = db.bookings.Join(db.users, u => u.userId, j => j.userId, (u, j) => new { booking = u, user = j }).ToList();
var Lists = demo.Select(i=> Mapper.Map<UserBookingModel>(demo)).ToList();
return View(Lists);
I am getting 2 rows in Lists variable which is same as demo Variable but when I check inside the List variable I am getting null value as per you can see in below image:
but if you see the demo variable, it shows the record
assuming that "UserBookingModel" is really your destination class and not your source class,
you had a mistake sending the whole "demo" object to the mapper instead of each row
var demo = db.bookings.Join(db.users, u => u.userId, j => j.userId, (u, j) => new {
booking = u, user = j }).ToList();
var Lists = demo.Select(i=> Mapper.Map<UserBookingModel>(i)).ToList();
return View(Lists);
Related
This is a .NET Core Web API Task method. I have a flat table that I need to convert into a nested DTOs. The first DTO works but I can't seem to get the second DTO to nest after grouping.
I know I have done the grouping correctly. I am just not sure the second level nesting of the DTO is done correctly, it complains about not being able to translate to some type.
LINQ Query to put data in a nested object
Can someone point me in the right track?
public async Task<List<PointCardViewModel>> GetPointCards() {
var data = (from s in db.Students
join dc in db.DailyCards on s.StudentId equals dc.StudentId
join dcli in db.DailyCardLineItems on dc.CardId equals dcli.CardId
join dcob in db.DailyCardOtherBehaviors on dc.CardId equals dcob.CardId
select new
{
s.StudentName,
s.StudentGrade,
dc.CardId,
dc.CardDate,
dcli.ClassParticipationPoints,
dcli.AssignmentCompletionPoints,
dcli.BonusHomeworkPoints,
dcli.ClassPeriod,
dcob.PersonalAppearancePoints,
dcob.LunchPoints,
dcob.RecessOtherPoints,
dcob.AmHomeroomPoints,
dcob.PmHomeroomPoints
});
var queryPointCards = (data
.GroupBy(x => new
{
x.CardId,
x.StudentGrade,
x.StudentName,
x.CardDate,
x.PersonalAppearancePoints,
x.LunchPoints,
x.RecessOtherPoints,
x.AmHomeroomPoints,
x.PmHomeroomPoints
})
.Select(x => new PointCardViewModel()
{
CardId = x.Key.CardId,
StudentName = x.Key.StudentName,
Grade = x.Key.StudentGrade,
EvaluationDate = x.Key.CardDate,
PersonalAppearancePoints = x.Key.PersonalAppearancePoints,
LunchPoints = x.Key.LunchPoints,
RecessOtherPoints = x.Key.RecessOtherPoints,
AMHomeRoomPoints = x.Key.AmHomeroomPoints,
PMHomeRoomPoints = x.Key.PmHomeroomPoints,
//LineItems = null --> This works!! But not the below
LineItems = x.Select(c => new LineItemViewModel
{
ClassPeriod = c.ClassPeriod,
BonusHomeworkPoints = c.BonusHomeworkPoints,
ClassParticipationPoints = c.ClassParticipationPoints,
AssignmentCompletionPoints = c.AssignmentCompletionPoints
})
}
)
).ToListAsync();
if (db != null)
{
return await queryPointCards;
}
return null;
}
You have hit limitation of Grouping. After groping you cannot access to group items. Only fields from 'Key' and aggregation functions are allowed.
So just put data.AsEnumerable() and do grouping on the client side.
I can't for the life of me figure out how to join these two tables on UserName using entity framework.
I tried both the statement and the method and neither worked.
The tables definitely have the same user in them
var employees = _context.Employees.Include(e => e.Loc);
//Only show employees with a user role of manager
var managerUsers = await _userManager.GetUsersInRoleAsync("Manager");
var match = (from e in employees
join m in managerUsers on e.UserName equals m.UserName
select new { Employee = e }).ToList();
So, short code breakdown I get a list of all employees from the database context. I look in user roles to find a list of users with the Manager role. Employee also has a UserName field, and I tried to join them using the UserName field. There is one manager currently returning correctly in both tables with a matching username, yet after this code, match has 0 results.
I also tried it like this:
employees.Join(managerUsers,
e => e.UserName,
m => m.UserName,
(e,m) => new { e }).ToList();
But that also doesn't return any records. What am I doing wrong?
Figured out a solution myself
var managerEmployees = new List<Employee>();
for(int a = 0; a< selectManagersList.Count(); a++)
{
var found = await _context.Employees.FirstOrDefaultAsync(u=> u.UserName == managerUsers.ElementAt(a).UserName);
if (found!=null)
{
managerEmployees.Add(found);
}
}
var list = oSIM.Issues.Join(db.IssueTracker_Read,
c => c.IssueId,
o => o.issueid,
(c, o) => new
{
c.read = o.issueid==null?false:true;
});
This is some pseudo code that doesn't work but should convey my requirement.
Entity of Issues is of type Issue which has many fields. I want to update Issue.Read to true if there is a linked record in IssueTracker_Read record.
The returned collection should be list but with list[x].read to be updated based on a linked record.
You can try something like this:
var list = oSIM.Issues.GroupJoin(db.IssueTracker_Read,
c => c.IssueId,
o => o.issueid,
(c, o) => new
{
Issue = c,
IssueRead = o.DefaultIfEmpty()
}).Select(groupJoinInfo=> new {
groupJoinInfo.Issue,
Read = groupJoinInfo.IssueRead != null && groupJoinInfo.IssueRead.Any()
});
And then you can iterate through the returned collection and update the Issues with the new Read property from the anonymous object.
GroupJoin performs an left join between the tables.
Edit
Added missing new, thanks user2520306.
Edit 2
Added a new condition for the Read property, this should return correctly.
Here's my code:
var myStrings = (from x in db1.MyStrings.Where(x => homeStrings.Contains(x.Content))
join y in db2.MyStaticStringTranslations on x.Id equals y.id
select new MyStringModel()
{
Id = x.Id,
Original = x.Content,
Translation = y.translation
}).ToList();
And I get the error that the specified LINQ expression contains references to queries that are associated with different contexts. I know that the problem is that I try to access tables from both db1 and db2, but how do I fix this?
MyStrings is a small table
Load filtered MyStrings in memory, then join with MyStaticStringTranslations using LINQ:
// Read the small table into memory, and make a dictionary from it.
// The last step will use this dictionary for joining.
var byId = db1.MyStrings
.Where(x => homeStrings.Contains(x.Content))
.ToDictionary(s => s.Id);
// Extract the keys. We will need them to filter the big table
var ids = byId.Keys.ToList();
// Bring in only the relevant records
var myStrings = db2.MyStaticStringTranslations
.Where(y => ids.Contains(y.id))
.AsEnumerable() // Make sure the joining is done in memory
.Select(y => new {
Id = y.id
// Use y.id to look up the content from the dictionary
, Original = byId[y.id].Content
, Translation = y.translation
});
You are right that db1 and db2 can't be used in the same Linq expression. x and y have to be joined in this process and not by a Linq provider. Try this:
var x = db1.MyStrings.Where(xx => homeStrings.Contains(xx.Content)).ToEnumerable();
var y = db2.MyStaticStringTranslations.ToEnumerable();
var myStrings = (from a in x
join b in y on x.Id equals y.id
select new MyStringModel()
{
Id = x.Id,
Original = x.Content,
Translation = y.translation
}).ToList();
Refer to this answer for more details: The specified LINQ expression contains references to queries that are associated with different contexts
dasblinkenlight's answer has a better overall approach than this. In this answer I'm trying to minimize the diff against your original code.
I also faced the same problem:
"The specified LINQ expression contains references to queries that are associated with different contexts."
This is because it's not able to connect to two context at a time so i find the solution as below.
Here in this example I want to list the lottery cards with the owner name but the Table having the owner name is in another Database.So I made two context DB1Context and DB2Context.and write the code as follows:
var query = from lc in db1.LotteryCardMaster
from om in db2.OwnerMaster
where lc.IsActive == 1
select new
{
lc.CashCardID,
lc.CashCardNO,
om.PersonnelName,
lc.Status
};
AB.LottryList = new List<LotteryCardMaster>();
foreach (var result in query)
{
AB.LottryList.Add(new LotteryCardMaster()
{
CashCardID = result.CashCardID,
CashCardNO = result.CashCardNO,
PersonnelName =result.PersonnelName,
Status = result.Status
});
}
but this gives me the above error so i found the other way to perform joining on two tables from diffrent database.and that way is as below.
var query = from lc in db1.LotteryCardMaster
where lc.IsActive == 1
select new
{
lc.CashCardID,
lc.CashCardNO,
om.PersonnelName,
lc.Status
};
AB.LottryList = new List<LotteryCardMaster>();
foreach (var result in query)
{
AB.LottryList.Add(new LotteryCardMaster()
{
CashCardID = result.CashCardID,
CashCardNO = result.CashCardNO,
PersonnelName =db2.OwnerMaster.FirstOrDefault(x=>x.OwnerID== result.OwnerID).OwnerName,
Status = result.Status
});
}
I have the following two objects:
User
class User {
public int role;
}
Role
class Role {
public int id;
public string name;
}
be note that role property inside User is int and not Role, that's our limitations.
I want to join between all the users and each of his role. In the mapping objects there is no reference as you can understand, just a simple type (int).
How do I do that join statement?
It's called a theta join:
var a = (from u in session.Query<User>()
from r in session.Query<Role>()
where u.role == r.id
select new { u.Username, Role = r.name }).ToList();
Assuming you have a Username property on the User class.
Yes, this "theta join" (as I just learned this term) is very handy and let's us not worry about putting in pointless mapping relationships.
WARNING HOWEVER IN USING THIS!!! This tripped me up a lot.
Adding to the above example...
var list = new List<int>( { 2, 3 } ); // pretend in-memory data from something.
var a =
(from u in session.Query<User>()
from x in list
from r in session.Query<Role>()
where u.role == r.id
where r.id == x.id // pretend list wants to limit to only certain roles.
select new { u.Username, Role = r.name }).ToList();
THIS WILL BOMB with some NotSupported exception.
The trick is that anything coming from NHibernate Session must come LAST. So this alteration WILL work:
var a =
(from x in list
from u in session.Query<User>()
from r in session.Query<Role>()
where u.role == r.id
where r.id == x.id // pretend list wants to limit to only certain roles.
select new { u.Username, Role = r.name }).ToList();
And and BTW, you can use join as well, however you have to make sure if you have any nullable data types, that you use the .Value if you are joining to something not-nullable.
var a =
(from x in list
from u in session.Query<User>()
join r in session.Query<Role>() on u.role equals r.id
where r.id == x.id // pretend list wants to limit to only certain roles.
select new { u.Username, Role = r.name }).ToList();
And while we're at it, let's say you have a method that has some dynamic condition. In this example the 'list' which could be a list of roles to filter by, but don't filter at all if the list is not there. Well, if you do the .ToList() then you are causing this query to execute immediately. But instead you can add a condition and then execute it later:
var a =
from u in session.Query<User>()
join r in session.Query<Role>() on u.role equals r.id
where r.id == x.id // pretend list wants to limit to only certain roles.
select new { u.Username, Role = r.name, RoleID = r.id }; // Adding the Role ID into this output.
if (list != null) // assume if the list given is null, that means no filter.
{
a = a.Where(x => list.Contains(x.RoleID));
// WARNING. Unfortunately using the "theta" format here will not work. Not sure why.
}
var b = a.ToList(); // actually execute it.
var c = a.Select(x => new { x.Username, x.Role }).ToList() // if you insist on removing that extra RoleID in the output.
One last thing.. Sometimes some simple logic will fail when executed in the select new { .. } part. I don't have an explanation. In our case the logic was just converting a DB value of a uint to an Enumerator of a model. But to get around that, I just avoided doing that conversion while reading the data but saved the value. Then in a later step, after the data was loaded, I just did the conversion in another LINQ statement.
DISCLAIMER: While I wrote many of these things all the past several weeks, I did not put this code into my compiler to verify 100%.