I want to get a list of my friends' stories. It didn't work through LINQ, but I was able to write a good SQL query that really works and returns what I need. I use .NET 7 & EF Core 7.
int userId = 1;
StoryContainerRto test = await _context.StoryContainer
.FromSqlInterpolated($#"SELECT s."Id", s."AuthorId", u."Id", u."AccountHeaderUrl", u."AvatarUrl", u."Description", u."Email", u."IsAuthorOfQualityContent", u."IsDeleted", u."IsInShadowBan", u."IsVerifiedProfile", u."LinkInBio", u."MedalsAmount", u."Name", u."Nickname", u."PasswordHash", u."PasswordSalt", u."PhoneNumber", u."PhoneNumberPrefix", u."PhoneNumberVerefied", u."RegistrationDateTime", u."TelegramId", u."TelegramVerifyingChatId"
FROM ""StoryContainer"" as s
INNER JOIN ""StoryContentRefs"" as scr ON scr.""StoryId"" = s.""Id""
LEFT JOIN ""User"" as u ON u.""Id"" = s.""AuthorId""
LEFT JOIN ""StoryContentRefRtoUserRto"" as whoView ON whoView.""ViewedId"" = {userId} AND whoView.""ViewedStoriesId"" = scr.""Id""
WHERE s.""AuthorId"" IN (
SELECT u.""Id""
FROM ""UserFriend"" as f, ""User"" as u
WHERE
CASE
WHEN f.""FirstUserFriendId"" = {userId}
THEN f.""SecondUserFriendId"" = u.""Id""
WHEN f.""SecondUserFriendId"" = {userId}
THEN f.""FirstUserFriendId"" = u.""Id""
END
)
AND scr.""CreateTimestamp"" >= NOW() - '1 day'::INTERVAL
AND scr.""IsDelete"" = false").ToListAsync();
Output:
System.ArgumentException: An item with the same key has already been added. Key: Id
If you execute this code, the SQL query will be identical (given that the SQL query is lightweight. It just gets the story and the author, but does not get the rest of the information, because it is needed only for clarity)
StoryContainerRto entity = await _context.StoryContainer
.AsNoTracking()
.Include(e => e.Author)
.Where(e => e.AuthorId == 1)
.ToListAsync();
Generated SQL (note the duplication of the "Id" column):
SELECT s."Id", s."AuthorId", u."Id", u."AccountHeaderUrl", u."AvatarUrl", u."Description", u."Email", u."IsAuthorOfQualityContent", u."IsDeleted", u."IsInShadowBan", u."IsVerifiedProfile", u."LinkInBio", u."MedalsAmount", u."Name", u."Nickname", u."PasswordHash", u."PasswordSalt", u."PhoneNumber", u."PhoneNumberPrefix", u."PhoneNumberVerefied", u."RegistrationDateTime", u."TelegramId", u."TelegramVerifyingChatId"
FROM "StoryContainer" AS s
INNER JOIN "User" AS u ON s."AuthorId" = u."Id"
WHERE s."AuthorId" = 1
User table:
[Table("User")]
public class UserRto
{
[Key] public int Id { get; set; }
[Required] public string Nickname { get; set; }
public string? Email { get; set; }
[Required] public byte[] PasswordHash { get; set; }
[Required] public byte[] PasswordSalt { get; set; }
public string? Name { get; set; }
public string? Description { get; set; }
public string? LinkInBio { get; set; }
public int MedalsAmount { get; set; }
public string? AvatarUrl { get; set; }
public bool IsDeleted { get; set; }
public bool? IsVerifiedProfile { get; set; }
public bool? IsAuthorOfQualityContent { get; set; }
public bool IsInShadowBan { get; set; }
public DateTime RegistrationDateTime { get; set; }
public string? PhoneNumberPrefix { get; set; }
public string? PhoneNumber { get; set; }
public bool PhoneNumberVerefied { get; set; }
public string? TelegramId { get; set; }
public string? TelegramVerifyingChatId { get; set; }
public string? AccountHeaderUrl { get; set; }
public List<FriendInvitationRto> FriendInvitationsSent { get; set; }
public List<FriendInvitationRto> FriendInvitationsReceived { get; set; }
public List<UserFriendRto> FirstFriends { get; set; }
public List<UserFriendRto> SecondFriends { get; set; }
public List<StoryContentRefRto> ViewedStories { get; set; }
public StoryContainerRto StoryContainer { get; set; }
}
Story table:
[Table("StoryContainer")]
public class StoryContainerRto
{
public int Id { get; set; }
public int AuthorId { get; set; }
public UserRto Author { get; set; }
public List<StoryContentRefRto> Items { get; set; }
}
How do I complete the request? I understand that the fact is that 3 columns of "Id" come from three tables. But at the same time, if you look at the request generated by EF itself, then there are also 2 "Ids". How do I execute such a request correctly?
https://makolyte.com/ef-core-select-queries-involving-multiple-table/
There is an example of code using INNER JOIN like mine. I do not know why the same approach does not work for me
I also applied the AS operator to all the "Id" columns, but in that case I get this error:
The required column 'Id' was not present in the results of a 'FromSql' operation
I was able to solve this problem using a direct SQL query to the database, and then analyzed the information myself
List<StoryRto> friendsStories = new();
using (NpgsqlCommand command = (NpgsqlCommand)(_context as PotokContext)!.Database.GetDbConnection().CreateCommand())
{
command.CommandText = $#"SELECT s.*, scr.*, u.*, whoView.""ViewedId"" as ""IViewThis""
FROM ""Stories"" as s
INNER JOIN ""StoryContentRefs"" as scr ON scr.""StoryId"" = s.""Id""
INNER JOIN ""User"" as u ON u.""Id"" = s.""AuthorId""
LEFT JOIN ""StoryContentRefRtoUserRto"" as whoView ON whoView.""ViewedId"" = 1 AND whoView.""ViewedStoriesId"" = scr.""Id""
WHERE s.""AuthorId"" IN (
SELECT u.""Id""
FROM ""UserFriend"" as f, ""User"" as u
WHERE
CASE
WHEN f.""FirstUserFriendId"" = 1
THEN f.""SecondUserFriendId"" = u.""Id""
WHEN f.""SecondUserFriendId"" = 1
THEN f.""FirstUserFriendId"" = u.""Id""
END
)
AND scr.""CreateTimestamp"" >= NOW() - '1 day'::INTERVAL
AND scr.""IsDelete"" = false
LIMIT {count}
OFFSET {skipCount}";
(_context as PotokContext)!.Database.OpenConnection();
using (var reader = command.ExecuteReader())
{
if (reader.HasRows)
{
while (reader.Read())
{
// Stories table
int storyId = reader.GetInt32(0);
int authorId = reader.GetInt32(1);
// StoryContentRefs table
int scrId = reader.GetInt32(2);
int scrStoryId = reader.GetInt32(3);
string scrStoryContentRef = reader.GetString(4);
bool scrIsDelete = reader.GetBoolean(5);
DateTime scrCreateTimestamp = reader.GetDateTime(6);
// UserTable
int userId = reader.GetInt32(7);
string userNickname = reader.GetString(8);
string? userEmail = reader.IsDBNull(9) ? null : reader.GetString(9);
// password hash and salt will not be included
string? userName = reader.IsDBNull(12) ? null : reader.GetString(12);
string? userDescription = reader.IsDBNull(13) ? null : reader.GetString(13);
string? userLinkInBio = reader.IsDBNull(14) ? null : reader.GetString(14);
int userMedalsAmount = reader.GetInt32(15);
string? userAvatarUrl = reader.IsDBNull(16) ? null : reader.GetString(16);
bool userIsDeleted = reader.GetBoolean(17);
bool? userIsVerifiedProfile = reader.IsDBNull(18) ? null : reader.GetBoolean(18);
DateTime userRegistrationDateTime = reader.GetDateTime(19);
bool? userIsAuthorOfQualityContent = reader.IsDBNull(20) ? null : reader.GetBoolean(20);
string? userPhoneNumber = reader.IsDBNull(21) ? null : reader.GetString(21);
string? userPhoneNumberPrefix = reader.IsDBNull(22) ? null : reader.GetString(22);
bool userPhoneNumberVerified = reader.GetBoolean(23);
string? userTelegramId = reader.IsDBNull(24) ? null : reader.GetString(24);
string? userTelegramVerifyingChatId = reader.IsDBNull(25) ? null : reader.GetString(25);
bool userIsInShadowBan = reader.GetBoolean(26);
string? userAccountHeaderUrl = reader.IsDBNull(27) ? null : reader.GetString(27);
// WhoViewStory relation
int? iViewThis = reader.IsDBNull(28) ? null : reader.GetInt32(28);
UserRto user = new()
{
Id = userId,
Nickname = userNickname,
Email = userEmail,
Name = userName,
Description = userDescription,
LinkInBio = userLinkInBio,
MedalsAmount = userMedalsAmount,
AvatarUrl = userAvatarUrl,
IsDeleted = userIsDeleted,
IsVerifiedProfile = userIsVerifiedProfile,
RegistrationDateTime = userRegistrationDateTime,
IsAuthorOfQualityContent = userIsAuthorOfQualityContent,
PhoneNumber = userPhoneNumber,
PhoneNumberPrefix = userPhoneNumberPrefix,
PhoneNumberVerefied = userPhoneNumberVerified,
TelegramId = userTelegramId,
TelegramVerifyingChatId = userTelegramVerifyingChatId,
IsInShadowBan = userIsInShadowBan,
AccountHeaderUrl = userAccountHeaderUrl
};
List<UserRto> viewed = new();
if (iViewThis != null) viewed.Add(user);
StoryContentRefRto storyContentRef = new()
{
Id = scrId,
StoryId = scrStoryId,
ContentRefs = scrStoryContentRef,
IsDelete = scrIsDelete,
CreateTimestamp = scrCreateTimestamp,
Viewed = viewed
};
if (friendsStories.FirstOrDefault(e => e.Id == scrStoryId) == null)
{
// Create new
StoryRto story = new()
{
Id = storyId,
AuthorId = authorId,
Author = user,
Items = new() { storyContentRef }
};
friendsStories.Add(story);
}
else
{
// Add to existing
StoryRto story = friendsStories.First(e => e.Id == scrStoryId);
story.Items.Add(storyContentRef);
}
}
}
else
{
Console.WriteLine("No rows found.");
}
}
}
I have this models
public class RoutingAttributeModel
{
public int Bus_No { get; set; }
public int Attribute_No { get; set; }
public string Attribute_Name { get; set; }
public string Status { get; set; }
public string Notes { get; set; }
}
public class AgentRoutingAttributeModel
{
public int Agent_No { get; set; }
public int Bus_No { get; set; }
public int Attribute_No { get; set; }
public string Attribute_Name { get; set; }
public string Status { get; set; }
}
List<RoutingAttributeModel> lstComplete = new List<RoutingAttributeModel>();
List<AgentRoutingAttributeModel> lstAssigned = new List<AgentRoutingAttributeModel>();
Filled this with some data
Is it possible to filter with Linq? I want to save in a new list the diferent content between lstComplete and lstAssigned
I was trying to join both lists but got stuck there
var results1 = from cl in lstComplete
join al in lstAssigned
on cl.Attribute_No equals al.Attribute_No
select cl;
you can use linq
as my understanding, you try to find linked by attribute_No records and have a list of not matching properties?
lstComplete.Add(new RoutingAttributeModel(){
Attribute_Name = "aaa",
Attribute_No = 1,
Bus_No = 1,
Notes = "",
Status = "status"
});
lstAssigned.Add(new AgentRoutingAttributeModel()
{
Attribute_No = 1,
Agent_No = 10,
Bus_No = 1,
Attribute_Name = "bbb",
Status = "status2"
});
var lst = lstComplete
.Join(lstAssigned,
complete => complete.Attribute_No,
assigned => assigned.Attribute_No,
(complete, assigned) => new { lstComplete = complete, lstAssigned = assigned })
.Select(s => new { s.lstComplete, s.lstAssigned})
.Where(w=>
w.lstAssigned.Attribute_Name != w.lstComplete.Attribute_Name
|| w.lstAssigned.Bus_No != w.lstComplete.Bus_No
)
.ToList()
.Dump();
so result would be
You could try the following query
var filteredList = lstComplete
.Where(x => !lstAssigned.Any(y => y.Attribute_No == x.Attribute_No));
I am having a class like this.
public class CameraModel
{
public int JobId { get; set; }
public int ViewId { get; set; }
public Guid ViewGuid { get; set; }
public string Name { get; set; }
public int ViewNum { get; set; }
public int LayoutID { get; set; }
public List<CameraViewItemModel> CameraViewItems { get; set; }
}
The CameraViewItemModel class is like this:
public class CameraViewItemModel
{
public int JobID { get; set; }
public Guid ViewGuid { get; set; }
public int ViewID { get; set; }
public int CamNum { get; set; }
public Guid ChannelGuid { get; set; }
public string Name { get; set; }
public ActionType Action { get; set; }
}
Now, I am assigning the list of CameraViewItemModel like this:
// get all the cameramodel's
cameraModels = _unitOfWork.Context.CameraViews.Where(m => m.JobId == siteId)
.Select(m => new CameraModel
{
JobId = m.JobId,
ViewId = m.ViewId,
ViewGuid = m.ViewGuid,
Name = m.Name,
ViewNum = m.ViewNum,
LayoutID = m.LayoutId
}).ToList();
// get all the cameraviewitemmodels
cameraViewItemModels =
(from cameraView in _unitOfWork.Repository<CameraViews>().Get(x => x.JobId == siteId).Result
join cameraViewItem in _unitOfWork.Repository<CameraViewItems>().Get(x => x.JobId == siteId)
.Result on cameraView.ViewId equals cameraViewItem.ViewId into CameraViewItemResults
from cameraViewItemResult in CameraViewItemResults.DefaultIfEmpty()
join cameraChannel in _unitOfWork.Repository<CameraChannels>().Get(x => x.JobId == siteId)
.Result on (cameraViewItemResult == null ? new Guid() : cameraViewItemResult.ChannelGuid) equals cameraChannel.ChannelGuid into CameraChannelResults
from cameraChannelResult in CameraChannelResults.DefaultIfEmpty()
select new CameraViewItemModel
{
JobID = cameraView.JobId,
ViewID = cameraView.ViewId,
ViewGuid = cameraView.ViewGuid,
CamNum = cameraViewItemResult.CamNum,
ChannelGuid = cameraChannelResult.ChannelGuid,
Name = cameraChannelResult.Name
}).ToList();
// then do a 'join' on JobId, ViewId and ViewGuid and assign the list of cameraviewitemmodels to cameraModels.
foreach (var cameraModel in cameraModels)
{
cameraModel.CameraViewItems = (from cameraViewItem in cameraViewItemModels
where cameraModel.JobId == cameraViewItem.JobID
&& cameraModel.ViewId == cameraViewItem.ViewID
&& cameraModel.ViewGuid == cameraViewItem.ViewGuid
select cameraViewItem).ToList();
}
return cameraModels;
There are three tables in database:
CameraViews, CameraViewItems, CameraChannels.
CameraViews is the main table. It is left joined with CameraViewItems and CameraChannels to get the desired result. There may not be any data in CameraViewItems and CameraChannels for a corresponding CameraView.
Is it possible to assign the list of CameraViewItemModels to CameraModels in a single linq statement.
Here is a simple way to add values to a sub list, dunno if this is what you mean. You can keep selecting sub lists if that is necessary.
var parent_lst = new List<List<string>>(); // Root/parent list that contains the other lists
var sub_lst = new List<string>(); // Sub list with values
var selected_parent_lst = parent_lst[0]; // Here I select sub list, in this case by list index
selected_parent_lst.Add("My new value"); // And here I add the new value
I have a query that needs to check the value from object list if it exists by loop through the value of the main object. How can recode below?
foreach (var kd in dto.KeyDriverModels)
{
var keyDriverModelNodeValue = result.SingleOrDefault(x => x.KeyDriverModelId == kd.ID);
kd.SelectionStatus = keyDriverModelNodeValue != null ?
keyDriverModelNodeValue.SelectionStatus : string.Empty;
}
I tried to model your code and rewrite the code as Linq. See if this works
static DTO dto = new DTO();
static void Main(string[] args)
{
List<KeyDriver> keyDrivers = new List<KeyDriver>();
List<KeyDriver> result = keyDrivers.Where(x => x.KeyDriverModelId > 1000).ToList();
foreach (var kd in dto.KeyDriverModels)
{
var keyDriverModelNodeValue = result.SingleOrDefault(x => x.KeyDriverModelId == kd.ID);
kd.SelectionStatus = keyDriverModelNodeValue != null ?
keyDriverModelNodeValue.SelectionStatus : string.Empty;
}
//new code
var kd1 = from r in result
join d in dto.KeyDriverModels
on r.KeyDriverModelId equals d.ID into drs
from dr in drs
select new { dr }.dr.SelectionStatus != null ? dr.SelectionStatus : string.Empty;
}
}
public class DTO
{
public List<KeyDriverModel> KeyDriverModels { get; set; }
}
public class KeyDriverModel
{
public int ID { get; set; }
public string SelectionStatus { get; set; }
}
public class KeyDriver
{
public int KeyDriverModelId { get; set; }
public string SelectionStatus { get; set; }
}
class user
{
public string userID { get; set; }
public string groupID { get; set; }
public int individualCredit { get; set; }
public int groupCredit { get; set; }
}
I have a list like this
List<user> listUsers = new List<user>();
I want to group users with same groupID.
Calculate groupCredit by adding the individualcredit s of each member in group and by dividing it by the number of group members.
Finally I want to assign each user with their groupCredit.
There are groups with three to five members.
How to do that?
Here's what I have tried.
var groupedUsers = from users in listUsers
where users.groupID != ""
group users by users.groupID into grouphold
select grouphold ;
Here's what I don't know.
How to search for the same groupID? In what I have tried I check for all Items groupID is blank.
Althought I agree with Sahil's comment, here is a starting point...
You can use LINQ, something like this:
List<user> listUsers = new List<user>();
public int groupUsersbyID(int _groupID)
{
var ListOfUsers = (from g in listUsers where g.groupID == _groupID select g).ToList();
var count = ListOfUsers.Count();
var totalCreditforGroup = 0;
var GroupCredit = 0;
foreach (var indidCredit in ListOfUsers)
{
totalCreditforGroup = totalCreditforGroup + indidCredit.individualCredit;
GroupCredit = totalCreditforGroup / count;
}
return GroupCredit;
}
public int returnGroupID(int userId)
{
var GroupIDforUser = (from i in listUsers where i.userID == userId select i.groupID).FirstOrDefault();
return GroupIDforUser;
}
public class user
{
public int userID { get; set; }
public int groupID { get; set; }
public int individualCredit { get; set; }
public int groupCredit { get; set; }
}