Develop Reference

LinqToDb: Rank is server-side method

I am trying to use linq2db.EntityFrameworkCore for some of its windowing functions, such as RANK().
Below is my implementation:
var abc = (from tl in _repo.Context.TransferLink
join tlt in _repo.Context.TransferLinkType on new { TLinkId = tl.TransferLinkTypeId, EType = "Deviance" } equals new { TLinkId = tlt.TransferLinkTypeId, EType = tlt.EnumTransferLinkType }
//let duplicateCount = _repo.Context.TransferLink.Where(tl1 => tl1.SecondaryTransferId != null && tl.SecondaryTransferId != null &&
//tl1.SecondaryTransferId == tl.SecondaryTransferId.Value).Count()
where
(allTransferIds.Contains(tl.PrimaryTransferId) || allTransferIds.Contains(tl.SecondaryTransferId)) &&
!tl.Archived
select new
{
TransferLinkId = tl.TransferLinkId,
TransferLinktypeId = tl.TransferLinkTypeId,
PrimaryTransferId = tl.PrimaryTransferId,
SecondaryTransferId = tl.SecondaryTransferId,
DuplicateCount = Sql.Ext.Count(tl.TransferLinkId)
.Over()
.PartitionBy(tl.SecondaryTransferId)
.ToValue()
UpdatedDate = tl.UpdatedDate,
RankVal = Sql.Ext.Rank()
.Over()
.PartitionBy(tl.TransferLinkTypeId, tl.SecondaryTransferId)
.OrderByDesc(tl.UpdatedDate)
.ThenBy(tl.TransferLinkId)
.ToValue()
}).ToList();
This code throws the exception:
Rank is server-side method
I have tried searching for a solution, but could not find any.
Any idea?

For using linq2db.EntityFrameworkCore you have to switch to library's LINQ provider. It can be done by simple ToLinqToDB() call.
var query = /* some EF Core query */
query = query.ToLinqToDB();
var result = query.ToList();

LINQ Dynamic Query with group by and string variable

I want to create a dynamic query with LINQ-to-SQL and everything works except for one thing: group by. I looked at the other questions but haven't found a reason so far why it does not work.
I use using System.Linq.Dynamic; with the following query (that works):
int numberOfRankedItems = 3;
string minMaxChoice = "max";
string orderBy = "";
if (minMaxChoice == "max")
{
orderBy = "queryGroup.Sum(row => row.POSITIONVALUE) descending";
} else if (minMaxChoice == "min")
{
orderBy = "queryGroup.Sum(row => row.POSITIONVALUE) ascending";
}
string minMaxFeatureColumnName = "BRANDNAME";
string selectMinMaxFeature = "new { minMaxFeature = queryGroup.Key." + minMaxFeatureColumnName + ", sumPosition = queryGroup.Sum(row => row.POSITIONVALUE)}";
var query = (from tableRow in Context.xxx
where /* some filters */
group tableRow by tableRow.BRANDNAME into queryGroup
orderby orderBy
select selectMinMaxFeature).Take(numberOfRankedItems).ToList();
The use of variables for orderby and select works fine, but for group by not no matter what I try to replace with a variable. The query actually works if I e.g. use a variable instead of tableRow.BRANDNAME but the query returns the wrong result. The goal is to be able to set the column for the grouping dynamically.
Ideas?
Thanks
Edit: there seem to be multiple issues also with the other variables. So I generalize the question a bit: how can I generalize the following query in terms of
The column to group by
The column to order by + ASC or DESC
In the select statement the columnname of the first statement (BRANDNAME)
Here is the query:
var query = (from tableRow in ctx.xxx
where /* filter */
group tableRow by new { tableRow.BRANDNAME } into queryGroup
orderby queryGroup.Sum(row => row.POSITIONVALUE) descending
select new { minMaxFeature = queryGroup.Key.BRANDNAME, sumPosition = queryGroup.Sum(row => row.POSITIONVALUE) }).Take(numberOfRankedItems).ToList();
Would be great without expression trees ;)

I have now elaborated a solution to the question:
The solution uses as before using System.Linq.Dynamic; allows now to set certain variables. In the end it returns a dictionary.
// set variables
int numberOfRankedItems;
if (queryData.NumberOfRankedItems != null)
{
numberOfRankedItems = (int) queryData.NumberOfRankedItems;
} else
{
numberOfRankedItems = 0;
}
string minMaxChoice = queryData.MinMaxChoice;
string minMaxFeatureColumnName = queryData.MinMaxFeatureColumnName;
string orderByPrompt = "";
if (minMaxChoice == "max")
{
orderByPrompt = "it.Sum(POSITIONVALUE) descending";
} else if (minMaxChoice == "min")
{
orderByPrompt = "it.Sum(POSITIONVALUE) ascending";
}
string groupByPrompt = queryData.MinMaxFeatureColumnName;
// execute query
IQueryable query = (from tableRow in Context.xxx
where /* some filters */
select tableRow).
GroupBy(groupByPrompt, "it").
OrderBy(orderByPrompt).
Select("new (it.Key as minMaxFeature, it.Sum(POSITIONVALUE) as sumPosition)").
Take(numberOfRankedItems);
// create response dictionary
Dictionary<int?, Dictionary<string, int?>> response = new Dictionary<int?, Dictionary<string, int?>>();
int count = 1;
foreach (dynamic item in query)
{
string minMaxFeatureReturn = item.GetType().GetProperty("minMaxFeature").GetValue(item);
int? sumPositionReturn = item.GetType().GetProperty("sumPosition").GetValue(item);
response[count] = new Dictionary<string, int?>() { { minMaxFeatureReturn, sumPositionReturn } };
count++;
}
return response;

How to solve error in LINQ: Data is null or empty

I have the following code. I want to check if the result is null with an if condition but it always shows an error. How to solve this?
string StrRefNo = Request.QueryString["ref"];
string[] SMSid = StrRefNo.Split('$');
DownloadsDbEntities db = new DownloadsDbEntities();
var data = (from d in db.SMSLink_Expiry
where d.RefNo == SMSid[0]
&& d.SMSLink.ID == Convert.ToInt32(SMSid[1])
select d).ToList();
if (data.Count > 0)
{
string ss = "yes";
}
The LINQ expression node type 'ArrayIndex' is not supported in LINQ to Entities.

Since the expression can not be translated into SQL, pull it out of the statement
string SMSId0 = SMSid[0];
int SMSId1 = Convert.ToInt32(SMSid[1]);
var data = (from d in db.SMSLink_Expiry
where d.RefNo == SMSId0
&& d.SMSLink.ID == SMSId1
select d).ToList();

This should fix your problem:
string StrRefNo = Request.QueryString["ref"];
string[] SMSid = StrRefNo.Split('$');
var ref = SMSid[0];
var smsLinkId = Convert.ToInt32(SMSid[1]);
DownloadsDbEntities db = new DownloadsDbEntities();
var data = (from d in db.SMSLink_Expiry
where d.RefNo == ref
&& d.SMSLink.ID == smsLinkId
select d).ToList();
if (data.Count > 0)
{
string ss="yes";
}
There are many things Linq does not support, since its translating the query to SQL internally.
For reference: The LINQ expression node type 'ArrayIndex' is not supported in LINQ to Entities

You can try this :
string[] SMSid = StrRefNo.Split('$');
var refno=SMSid[0];
var id=Convert.ToInt32(SMSid[1];
DownloadsDbEntities db = new DownloadsDbEntities();
var data = (from d in db.SMSLink_Expiry
where d.RefNo == refno
&& d.SMSLink.ID == id)
select d).ToList();

Linq to SQL - Ignore search parameters that are null or zero

I have a search form where the user can enter one to many parameters (Data, Status, Type, ID, Summary, Description) and leave the rest blank.
Here's my Linq to SQL code for my basic search. Is there a way to check each parameter within the Linq for zero, null or empty string?
List<RequestStatusModel> objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where r.CustomerID == 31
select (new RequestStatusModel
{
RequestID = r.RequestID,
RequestTitle = r.RequestTitle,
DateAdded = r.DateAdded.ToString(),
DateChanged = r.DateChanged.ToString(),
RequestStatusID = r.StatusID
});
Thank you!

If it doesn't have to be in your linq statement you could just do it with classic if statements.
List<RequestStatusModel> objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where r.CustomerID == 31
select (new RequestStatusModel
{
//...
});
if(data != null) //Replace with additional checks, if neccessary
{
query = query.where(x=> ...);
}
if(status != null)
{
query = query.where(x => ...)
}

If you want to only filter if certain criteria is passed, you should do something like this
var objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where r.CustomerID == 31
if (String.IsNullOrEmpty(r.RequestID))
objRequestStatus = objRequestStatus.Where(x => x.RequestID == r.RequestID);
if (String.IsNullOrEmpty(r.RequestTitle))
objRequestStatus = objRequestStatus.Where(x => x.RequestTitle == r.RequestTitle);
//you other filters here
This sets up the expression to what you want based on which requests are passed

If you want to avoid all those ifs, you could do
List<RequestStatusModel> objRequestStatus = new List<RequestStatusModel>();
var query = from r in SimCareDB.Requests
where (r.CustomerID == 31) &&
(!String.IsNullOrEmpty(id) ? r.RequestID == id : true) &&
(!String.IsNullOrEmpty(status) ? r.StatusID == status : true)
/* And so on */
select (new RequestStatusModel
{
RequestID = r.RequestID,
RequestTitle = r.RequestTitle,
DateAdded = r.DateAdded.ToString(),
DateChanged = r.DateChanged.ToString(),
RequestStatusID = r.StatusID
});

Linq not in select on datatable

Hi i've got 2 data tables (bannedlist,countrylist), both contains list of country names and cods in columns cc and country. I am trying to do a query where i can select countries from countrylist table that are not in bannedlist table in order to create a 3rd table.
Any ideas?
I haven't got too far with this.
var ccList = ds.Tables[2].AsEnumerable();
var bannedCCList = ds.Tables[1].AsEnumerable();
var query = from r in ccList....
..
after trying
var bannedCCList = ds.Tables[1].AsEnumerable();
var query = from r in ccList where !bannedCCList.Any(b => b["cc"] == r["cc"])select r;
i still get same country list. banned ones haven't been removed. here is more detail in order to explain more. not sure what i am doing wrong
protected void BindCountryBan(string subd)
{
DataSet ds = new DataSet();
ds = new DB().CountryBan_GetSiteSettings();
BannedCountryListBox.DataSource = ds.Tables[1];
BannedCountryListBox.DataValueField = "cc";
BannedCountryListBox.DataTextField = "country";
BannedCountryListBox.DataBind();
//bind country list
var ccList = ds.Tables[2].AsEnumerable();
var bannedCCList = ds.Tables[1].AsEnumerable();
var query = from r in ccList where !bannedCCList.Any(b => b["cc"] == r["cc"])select r;
//var query = ccList.Except(bannedCCList);
//CountryListBox.DataSource = ds.Tables[2];
DataTable boundTable = query.CopyToDataTable<DataRow>();
CountryListBox.DataSource = boundTable;
CountryListBox.DataValueField = "cc";
CountryListBox.DataTextField = "country";
CountryListBox.DataBind();
}

Except would work if you use it on sequences of the countries:
using System.Linq;
...
var ccList = from c in ds.Tables[2].AsEnumerable()
select c.Field<string>("Country");
var bannedCCList = from c in ds.Tables[1].AsEnumerable()
select c.Field<string>("Country");
var exceptBanned = ccList.Except(bannedCCList);
If you need the full rows where the countries aren't banned, you could try a left outer join:
var ccList = ds.Tables[2].AsEnumerable();
var bannedCCList = ds.Tables[1].AsEnumerable();
var exceptBanned = from c in ccList
join b in bannedCCList
on c.Field<string>("Country") equals b.Field<string>("Country") into j
from x in j.DefaultIfEmpty()
where x == null
select c;

You can use the Except() LINQ extension method like this:
var result = full.Except(banned);
However this will work fine with the default comparer of the contained type. Thus if you want to use a specific column like in your example, you might need another approach like:
from r in ccList
where !bannedCCList.Any(b => b["cc"] == r["cc"])
select r;
Using Except() implies the references are the same in both collections, which I think is not the case with Tables, or correct me if I'm wrong.

Try this:
var query = ccList.Except(bannedCCList);