I need to get index in my select statement.
My code:
IQueryable grpdRows;
dtInput = ds.Tables[0];
grpdRows = dtInput
.Select("", "partno")
.AsQueryable()
.GroupBy("new (iif(it[\"partno\"] == null, \"\", it[\"partno\"]) as GrpKey1)","it")
.Select("new (it.Key.GrpKey1 as GrpKey1, it.Count() as TotalCount")");
how to get index in select statement example:
.Select("new (it.Key.GrpKey1 as GrpKey1, it.Count() as TotalCount, **it.Index**")");
I'm not sure that this is possible via Dynamic Linq, but as workaround you can try something like this:
IQueryable grpdRows;
dtInput = ds.Tables[0];
grpdRows = dtInput
.Select("", "partno")
.AsQueryable()
.GroupBy("new (iif(it[\"partno\"] == null, \"\", it[\"partno\"]) as GrpKey1)","it")
.Select("new (it.Key.GrpKey1 as GrpKey1, it.Count() as TotalCount)");
var res = (from dynamic row in grpdRows
select row).Select((row,index)=>new {row.GrpKey1, row.TotalCount, Index=i});
Related
I am creating a result object from my query, something like this:
var result = from m in MyTable
join r in some_more_tables
select new ResultSummmary
{
Description = m.Description,
start_date = r.start_dat
};
But based on some condition before I get to this query and SELECT NEW, I want to be able to flex what I put in its Description filed, currently it is always m.Description but sometimes I want it to be a static text like "Hospital" and the rest of the times I want it to be m.Description as it is now.
How can we write it that way to be flexible?
Let's pretend the condition is stored in a variable called condition. This would allow you to write the following
var result = from m in MyTable
join r in some_more_tables
select new ResultSummmary
{
Description = condition ? m.Description : "Hospital",
start_date = r.start_dat
};
select new ResultSummmary
{
Description = someBool ? m.Description : "Hospital",
start_date = r.start_dat
};
I see Dynamic linq in below link:
ScottGu
I want to use this method to select a dynamic query like this:
I have a complex select and this way not solve my problem,
this is my select:
Select sUserName,sname, sFamily,sMobail,sid,sNumberSt,sActive,sPic,sDate from Student where {0} order by sid desc";
which {0} is a complex Condition:
sname like %somthing% and susername=N'something' and sid in (select sidfk from tablex where userteacher=N'name1')
and this condition is passed to method.
I must say that:
I don's know my condition,my condition specified with user search params.this condition that I say,Is only one example of what I want to do.
How can I do this?
Only way that solve my problem:
I send tow parameters instead of one,one for student and one for tablex:
var az = db.tablex.Where(p => p.userteacher== name1)
.Select(p => p.sidfk).ToList();
var query = db.Students.Where(textSearch).Where(s=>az.Contains(s.sid)).OrderByDescending(s => s.sid)
.Select(s => new
{
s.sUserName,
s.sname,
s.sFamily,
s.sMobail,
s.sid,
s.sNumberSt,
s.sActive,
s.sPic,
s.sDate,
});
wiche textSearch is :
sname like %somthing% and susername=N'something'
with dynamic linq
any better way is exist?
You don't need to use dynamic linq for this situation.
string paramA = "", paramB = "";
var query = from x in context.table1
where x.name == paramA
where context.table2.Where(y => y.field1 == paramB).Any(y => y.id == x.id)
select x;
Dynamic Linq usually use if in query you don't know what field will be use, so in your sample you use only params for conditions with field, so you don't ned dynamic linq
you can little optimize you query like this
var query = from student in db.Students
join teacher in db.tablex on student.sid equals teacher.sidfk
where student.sname.Contains('somthing') &&
susername=='something' &&
teacher.userteacher=='name1'
orderby s.sid descending
select new
{
s.sUserName,
s.sname,
s.sFamily,
s.sMobail,
s.sid,
s.sNumberSt,
s.sActive,
s.sPic,
s.sDate,
};
I have a DataTable. I would like to filter DataRows where City = "Hongkong".
How to apply LINQ against DataRow?
You could use the following Query
var filter = testTable.AsEnumerable().
Where(x => x.Field<string>("City") == "HongKong");
var result = dr.Where(r => r.Field<string>("City") == "Hongkong");
Using LINQ to DataSets, you can do the following:
DataTable table;
var rows =
from row in table.AsEnumerable()
where row.Field<string>("City") == "Hongkong"
select row;
Let's ay I have this query:
var results = from row in db.Table select row;
How can I access this:
string name = results[0]["columnName"];
if you really want a particular index you can use the Skip() method with First().
var rowOffset = 0;
var results = (from row in db.Table
select row).Skip(rowOffset).First()["columnName"];
But unless you are using a Where clause I would really recommend using the indexer. The indexer is pretty much a direct reference while the LINQ statement would be using the objects iterator.
Also don't forget you can do much more advanced stuff with LINQ.
var rowOffset = 0;
var pageLength = 10;
var results = (from row in db.Table
let colValue = row["columnname"]
where colValue != null
select colValue.ToString()
).Skip(rowOffset)
.Take(pageLength)
.ToArray();
var commaString = string.Join(", ", results);
If you specifically just want the zeroth element, you can use results.First()
results is a IEnumerable list of Rows. So you can get it with a simple foreach.
foreach(var row in results)
{
string name = row["columnName"];
}
(from row in db.Table select row).First().columnName
What do I put in my order by?? I want to order by Name. I have moved the orderby after the distinct because I read that it needs to be done last.
var result = (from r in db.RecordDocs
where r.RecordID == recordID
select new
{
DocTypeID = r.Document.DocType.DocTypeID,
Name = r.Document.DocType.Name,
Number = r.Document.DocType.Number
}
).Distinct().OrderBy( );
Just do
.OrderBy(doc => doc.Name)
Another option, if you really prefer the query expression syntax would be to chain your query construction across multiple statements:
var query = from r in db.RecordDocs
where r.RecordID == recordID
select new
{
DocTypeID = r.Document.DocType.DocTypeID,
Name = r.Document.DocType.Name,
Number = r.Document.DocType.Number
};
query = query.Disctinct();
query = from doc in query orderby doc.Name select doc;
Since all of these methods are deferred, this will result in the exact same execution performance.