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Is it possible to Pivot data using LINQ?
I'm wondering if its at all possible to create crosstab style results with Linq.
I have some data that looks like the following:
var list = new[]
{
new {GroupId = 1, Country = "UK", Value = 10},
new {GroupId = 1, Country = "FR", Value = 12},
new {GroupId = 1, Country = "US", Value = 18},
new {GroupId = 2, Country = "UK", Value = 54},
new {GroupId = 2, Country = "FR", Value = 55},
new {GroupId = 2, Country = "UK", Value = 56}
};
and I'm trying to output to a repeater control something like the following:
GroupId.....UK.....FR.....US
1...........10.....12.....18
2...........54.....55.....56
Its the dynamic columns that are causing my problems. Any solutions to this?
You need a runtimy class to hold these runtimy results. How about xml?
XElement result = new XElement("result",
list.GroupBy(i => i.GroupId)
.Select(g =>
new XElement("Group", new XAttribute("GroupID", g.Key),
g.Select(i => new XAttribute(i.Country, i.Value))
)
)
);
Are you expecting multiple records per result cell? If so there would need to be some Summing (and more grouping) in there.
(this answer is proof of concept, not final result. There's several issues to address, such as: ordering of columns, missing cells, and so on).
After doing a quick search you might want to look at the ModuleBuilder, TypeBuilder, and FieldBuilder classes in System.Reflection.Emit. They allow you to create a class dynamically at runtime. Outside of that you would need to do grouping on your objects and then do something with the hierarchical results you get from LINQ. I am not sure of a way to dynamically create anonymous type fields at runtime, and that sounds like what would need to happen.
You could try using the dynamic linq library provided by MS. They have a number of overloads to extensions methods that take strings as arguments. They also have an expression parser that takes a string an emits a lambda expression. You should be able to create a dynamic select using them.
A word of warning though, you end up with a non-generic IQueryable rather than a generic IQueryable so you are a little bit limited on what you can do with the result, and you give up a bit of type safety, but that may be OK in your application...
The link for the dynamic linq stuff is
http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx
There is a link where you can download the source code the the dynamic library, plus some nice illustrations of how you can use it.
var labResults = from lab in CoreLabResults
where lab.Patient == 8
group lab by new { lab.Patient, lab.TestNo, lab.CollectedDate }
into labtests
select new
{
labtests.Key.Patient,
labtests.Key.TestNo,
labtests.Key.CollectedDate,
MCHC = labtests.Where(lab => lab.TestVar == "MCHC").FirstOrDefault().Result,
LYABS = labtests.Where(lab => lab.TestVar == "LYABS").FirstOrDefault().Result,
TotalTests = labtests.Count()
}
Related
I have a list of strings like this
"Users": [
"usrName|Fullname|False|0|False|False",
"usrName|Fullname|False|0|False|False",
"usrName|Fullname|False|0|False|False",
"usrName|Fullname|False|0|False|False",
"usrName|Fullname|False|0|False|False",
]
In my episerver/optimizely code I want to match items. I have written this line of code
searchResult.Filter(x => x.Users.MatchContained(k=> k.Split('|')[3], "0"));
I am trying to get all Users where after splitiing on 'pipe' I get 0 at index 3. I am not getting the result, infact I get an exception.
What am I doing wrong here?
Since you left out A LOT of details these are my assumptions
Users is an IList<string> Users
You are trying to get all Users within that list/array where index 3 equals 0
What we don't know is, among others
Is there more than one page instance that have the Users instance filled?
Anyway, this cannot be solved using any Find API with the current system design. Instead you need to rely on linq to parse the result, but then the Find implementation may not be necessary.
var searchClient = SearchClient.Instance;
var search = searchClient.Search<BlogPage>();
var result = search.GetContentResult();
var usersResult = result
.SelectMany(x => x.Users)
.Where(x => x.Split('|')[3].Equals("0"));
This would create and return an object similar to this, since I'm using SelectMany the array would contain all users throughout the systems where there are matched pages from the search result.
If you for whatever reason would like to keep or see some page properties there are alternative approaches where you construct a new object within a select and remove any object where there where not matched users
var searchClient = SearchClient.Instance;
var search = searchClient.Search<BlogPage>();
var result = search.GetContentResult();
var usersResult = result
.Select(p => new
{
PageName = p.Name,
ContentLink = p.ContentLink.ToString(),
Users = p.Users.Where(x => x.Split('|')[3].Equals("0"))
})
.Where(x => x.Users.Any());
If you like to keep using Find for this kind of implementations you must store the data in a better way than strings with delimiters.
I try to find some references on LINQ with dynamic added strong types, static I have as in example:
var rowColl = _data.AsEnumerable();
var json = (from r in rowColl
select new
{
name = r.Field<string>("name"),
id = r.Field<int>("id"),
}).ToList();
Now where I am interested in if its possible to make "name" and "id" dynamic added on runtime as the information is available in the DataTable "_data", I think there is a simple solution for this however cant find any references on this
It's better practice to avoid using "var" as your type when possible. It looks like rowColl is of type IEnumerable<DataRow>. If that's true, then I would look to see what you can use in the DataRow class (see msdn documentation).
Given that rowColl is actually IEnumerable<DataRow>... If the columns are always going to be in the same order, then you could just do something like r[0] and r[1] in your select statement, i.e.
var json = (from r in rowColl
select new
{
name = r[0], // Where 0 is the index of the "name" column
id = r[1],
}).ToList();
If it complains at you for type-safety, then you could use int.Parse() to cast the string to an int and use the .ToString() extension on your columns instead.
I have a newbie LINQ question. I need to create two objects of same type from a list of strings. I need to append a text 'Direct' & "Indirect' to the string and use them as ID to create the two unique objects.
var vStrings = new List { "Milk", "Eggs", "Cheese" };
var vProducts = (from s in vStrings
select new Product { ID = s + "-Direct" })
.Union(
from s in vStrings
select new Product { ID = s + "-InDirect" });
You can see in the example above, I am using a Union to create two different objects, Is there a better way to rewrite this LINQ query?
Thanks for your suggestions
If you ever needed more suffixes, this might be a better way:
var strings = new List<string> { "Milk", "Eggs", "Cheese" };
var suffixes = new List<string> {"-Direct", "-InDirect"};
var products = strings
.SelectMany(_ => suffixes, (x, y) => new Product() {ID = x + y});
And it would only iterate over the original set of strings once.
This way isn't much shorter but I think it would be a little better such as there is only one Concat instead of many Union:
var vProducts2 = (from s in vStrings
select s + "-Direct").Concat(
from s in vStrings
select s + "-InDirect");
I have a list of customer id's, custList(of string).
I want to use a LINQ query to a Dataset, to get all customers in the customer table, where customerID is "IN" my custList(of string).
Is this possible in LINQ? I have searched online and not found the answer. I'm new to LINQ..
Thanks
In LINQ you use the Contains() method to perform these kind of queries.
I don't know LINQ to DataSets, but in LINQ to SQL you can do the following:
var statuses = new int[] {1, 2, 3};
var query = from p in dataContext.Products
where statuses.Contains(p.Id)
select p;
This should generate SQL similar to:
select * from Product p
where p.Id in (1, 2, 3)
(Note how it feels back-to-front in the LINQ code to the generated SQL - that's why if you know SQL well it's not very intuitive, but it makes very elegant use of existing .NET language features)
This also typically works for string and collections of some other basic types that L2S knows about because they're in the framework.
var custList = new HashSet<string>() { "a", "b", "c"...};
from record in table.ToEnumerable()
where custList.Contains(record.Field<string>("customerID"))
var custList = new HashSet<int> { 10, 15, 17 };
CustomerSet.Where(c => custList.Contains(c.CustomerID));
I have a single table and I need to build a bunch of nested objects based on the single table.
Data:
PointA PointB Month Time Price
1 2 11 11:00 10.99
1 2 12 11:00 9.99
Objects are
POINTS {PointA, PointB, Details}
Details {Month, ExtraDetails}
ExtraDetails {Time, Price}
I want to avoid having loads of loops and if statements, so should be able to use linq to do this. but its beyond my linq experience.
edit: These need grouping aswell
any help would be great.
Thanks
Just tried out a solution:
var nestedObjects = from row in data
select new {row.PointA, row.PointB, Details = new {
row.Month, ExtraDetails = new {
row.Time, row.Price
}
}};
This is assuming that you have already got your data into data.
Group by
If you want to group the Points together, you need 'Group By':
var nestedObjects = from row in data
group row by new { row.PointA, row.PointB } into Points
select new {
Points = Points.Key,
Details = from details in Points
select new { row.Month, ExtraDetails = new {
row.Time, row.Price
}}
};
A little more complicated - of course you might want to group by month as well, in which case, you need to follow the same pattern as for the Points bit. Note, this will not create tables, because the group by doesn't quite do that, but it at least creates the structure for you.
Assuming you got your classes defined for the objects you mentioned, and you have a constructor or properties so you can propery create the object in one line you could have a LINQ query returning a list of a POINTS.
If would go something lik this :
var res =
from item in table.AsEnumerable()
select new Points(){PointA = item["PointA"];
PointB = item["PointB"];
Details = from item2 in table.AsEnumberable()
where item["PointA"] = item2["PointA"] and item["PointB"] = item2["PointB"]
select new Details(){
month=item2["month"],
extraDetails = from item3 in table.AsEnumerable()...
}
};
At the end res will be a IEnumerable of Points
I am sorry for the code, I am not at a computer with .NET 3.5 so I cannot write a proper testable query