I'm working on refactoring some code to practice LINQ. For some reason I can't get this code to cooperate.
//ActionControls is a ControlCollection
var actionControls = flowLayoutPanel1.FilterControls(c => c is Button);
//TODO: Optimize
foreach(var control in actionControls)
{
control.Visible = workingItemDataTable.AsEnumerable().Any(row => "btn" + row.Field<string>("Name") == control.Name);
}
What I am trying to do now.
flowLayoutPanel1.FilterControls(c => c is Button && c.Name == "btnTaskInfo"//btnTaskInfo is always visible
|| workingItemDataTable.AsEnumerable().Any(row => "btn" + row.Field<string>("Name") == c.Name)).Cast<Button>()
But after casting this as a button, I can not figure out how to set visible = false. Any Advice?
You'd still need to iterate the controls, but you can probably do this, assuming FilterControls isn't much more than an alias for Where:
var actionControls = flowLayoutPanel1.OfType<Button>();
There are some "tricks" and shortcuts for iterating and doing sets within a lambda expression, but it makes the code just look messy and they are mostly just hacks. You can create your own extension ForEach (if there isn't one available to you if you really want to do it anyway).
flowLayoutPanel1.OfType<Button>().ForEach(btn=>{btn.Visible= ... });
Related
I see this all over the web, however I'm curious if there isn't an easier way to write this in lambda?
var x = from c in db.Client
from p in db.Prospects
from ct in db.Countys
select new ViewModelExcelReport
{
client = c.ClientName,
cntyCounty = ct.County,
sctSection = p.Section
};
I would like to see a lambda expression that does NOT use joins, as though i am almost certain that i have seen one without the joins, but if this isn't possible ofcouse i'd like to see one with, thanks.
Basically multiple from clauses contribute SelectMany calls. So your code is something like:
var x = db.Client
.SelectMany(c => db.Prospects, (c, p) => new { c, p })
.SelectMany(z => db.Countys, (z, ct) => new { z, ct })
.Select(zz => new ViewModelExcelReport
{
client = zz.z.c.ClientName,
cntyCounty = zz.ct.County,
sctSection = zz.z.p.Section
});
Note how this is rather more longwinded than the query expression - the compiler takes care of keeping track of all the range variables via transparent identifiers. Why do you want this in lambda form? What do you see as being the benefit? The query expression will be translated into exactly the same code, so you should use whichever one is clearer - which in this case looks like the query expression, IMO.
As an aside, I'd strongly recommend that you change your property names (in ViewModelExcelReport) to more idiomatic ones if you possibly can.
Is there anyway to change the following 2 linq expressions into 1?
var criticalCategories =
_commonDao.GetAllByExpression<CategoryItem>(
x => x.Category.Uid == gridAnswer.ActivityCategory.Uid && x.Critical);
if(criticalCategories.Any())
{
criticalWeight = criticalCategories.Min(x => x.Weight);
}
You can use Enumerable.DefaultIfEmpty to make sure that Min will produce a specific value if your source sequence contains no elements.
You could then write:
var criticalCategories = _commonDao.GetAllByExpression<CategoryItem>(...);
criticalWeight = criticalCategories
.Select(x => x.Weight)
.DefaultIfEmpty(42)
.Min();
The above is trivially chainable, but I did not actually chain it here because I 'm not quite sure how criticalCategories is supposed to be used later on (if at all). Could you please clarify?
All,
I've got the following code, and looking into ways to improve its readibility (and remove the null check) by using Linq.
var activePlan = CurrentPlans.First();
var activeObjectives = activePlan != null ? activePlan.Objectives : null;
The closest I get is the following:
var activeObjectives = CurrentPlans.Take(1).Select(x => x.Objectives);
which gives me a collection of x.Objectives instead of Objectives.
Any ideas?
I'd write if like this:
var activeObjectives = CurrentPlans.Select(x => x.Objectives).FirstOrDefault();
This way, it's easier to work out the intention by the use of methods. Take the first set of objectives, otherwise the default (null assuming Objectives refers to a reference type). Using SelectMany() for this case isn't the best choice IMO.
oh got it:
var activeObjectives = CurrentPlans.Take(1).SelectMany(x => x.Objectives)
http://msdn.microsoft.com/en-us/library/system.linq.enumerable.selectmany.aspx
I want to do something like DELETE FROM TABLE WHERE ID NOT IN (1,2,3) AND PAGEID = 9
I have a List of IDS but that could be changed if needs be. I can't work out how to get a boolean result for the LINQ parser.
Here is what Subsonic expects I think.
db.Delete(content => content.PageID == ID).Execute();
I can't work out how to do the NOT IN statement. I've tried the List.Contains method but something not quite right.
UPDATE: One alternative is to do:
var items = TABLE.Find(x => x.PageID == ID)'
foreach(var item in items)
{
item.Delete();
}
This hits the database a lot more though
When you say "something not quite right" what exactly do you mean?
I'd expect to write:
List<int> excluded = new List<int> { 1, 2, 3 };
db.Delete(content => !excluded.Contains(content.PageID)).Execute();
Note that you need to call Contains on the array of excluded values, not on your candidate. In other words, instead of saying "item not in collection" you're saying "collection doesn't contain item."
Try .Contains:
db.Delete(content => content.PageID.Contains(<Array containing ID's>).Execute();
(the above is just an example, might need some polishing for your specific situation)
I have found that this works but its not via LINQ
var table = new WebPageContentTable(_db.DataProvider);
var g = new SubSonic.Query.Delete<WebPageContent(_db.DataProvider)
.From(table)
.Where(table.ID)
.NotIn(usedID)
.Execute();
I have found that this does work and via LINQ - however it hits the database multiple times.
var f = WebPageContent.Find(x => !usedID.Any(e => e == x.ID));
if (f.Count > 0)
{
var repo = WebPageContent.GetRepo();
repo.Delete(f);
}
This I imagine would work in one hit to the database but I get an exception thrown in QueryVisitor::VisitUnary
WebPageContent.Delete(x => !usedID.Any(e => e == x.ID));
I felt like the following should be possible I'm just not sure what approach to take.
What I'd like to do is use the include method to shape my results, ie define how far along the object graph to traverse. but... I'd like that traversal to be conditional.
something like...
dealerships
.include( d => d.parts.where(p => p.price < 100.00))
.include( d => d.parts.suppliers.where(s => s.country == "brazil"));
I understand that this is not valid linq, in fact, that it is horribly wrong, but essentially I'm looking for some way to build an expression tree that will return shaped results, equivalent to...
select *
from dealerships as d
outer join parts as p on d.dealerid = p.dealerid
and p.price < 100.00
outer join suppliers as s on p.partid = s.partid
and s.country = 'brazil'
with an emphasis on the join conditions.
I feel like this would be fairly straight forward with esql but my preference would be to build expression trees on the fly.
as always, grateful for any advice or guidance
This should do the trick:
using (TestEntities db = new TestEntities())
{
var query = from d in db.Dealership
select new
{
Dealer = d,
Parts = d.Part.Where
(
p => p.Price < 100.0
&& p.Supplier.Country == "Brazil"
),
Suppliers = d.Part.Select(p => p.Supplier)
};
var dealers = query.ToArray().Select(o => o.Dealer);
foreach (var dealer in dealers)
{
Console.WriteLine(dealer.Name);
foreach (var part in dealer.Part)
{
Console.WriteLine(" " + part.PartId + ", " + part.Price);
Console.WriteLine
(
" "
+ part.Supplier.Name
+ ", "
+ part.Supplier.Country
);
}
}
}
This code will give you a list of Dealerships each containing a filtered list of parts. Each part references a Supplier. The interesting part is that you have to create the anonymous types in the select in the way shown. Otherwise the Part property of the Dealership objects will be empty.
Also, you have to execute the SQL statement before selecting the dealers from the query. Otherwise the Part property of the dealers will again be empty. That is why I put the ToArray() call in the following line:
var dealers = query.ToArray().Select(o => o.Dealer);
But I agree with Darren that this may not be what the users of your library are expecting.
Are you sure this is what you want? The only reason I ask is, once you add the filter on Parts off of Dealerships, your results are no longer Dealerships. You're dealing in special objects that are, for the most part, very close to Dealerships (with the same properties), but the meaning of the "Parts" property is different. Instead of being a relationship between Dealerships and Parts, it's a filtered relationship.
Or to put it another way, if I pull a dealership out of your results and passed to a method I wrote, and then in my method I call:
var count = dealership.Parts.Count();
I'm expecting to get the parts, not the filtered parts from Brazil where the price is less than $100.
If you don't use the dealership object to pass the filtered data, it becomes very easy. It becomes as simple as:
var query = from d in dealerships
select new { DealershipName = d.Name,
CheapBrazilProducts = dealership.Parts.Where(d => d.parts.Any(p => p.price < 100.00) || d.parts.suppliers.Any(s => s.country == "brazil")) };
If I just had to get the filtered sets like you asked, I'd probably use the technique I mentioned above, and then use a tool like Automapper to copy the filtered results from my anonymous class to the real class. It's not incredibly elegant, but it should work.
I hope that helps! It was an interesting problem.
I know this can work with one single Include. Never test with two includes, but worth the try:
dealerships
.Include( d => d.parts)
.Include( d => d.parts.suppliers)
.Where(d => d.parts.All(p => p.price < 100.00) && d.parts.suppliers.All(s => s.country == "brazil"))
Am I missing something, or aren't you just looking for the Any keyword?
var query = dealerships.Where(d => d.parts.Any(p => p.price < 100.00) ||
d.parts.suppliers.Any(s => s.country == "brazil"));
Yes that's what I wanted to do I think the next realease of Data Services will have the possiblity to do just that LINQ to REST queries that would be great in the mean time I just switched to load the inverse and Include the related entity that will be loaded multiple times but in theory it just have to load once in the first Include like in this code
return this.Context.SearchHistories.Include("Handle")
.Where(sh => sh.SearchTerm.Contains(searchTerm) && sh.Timestamp > minDate && sh.Timestamp < maxDate);
before I tried to load for any Handle the searchHistories that matched the logic but don't know how using the Include logic you posted so in the mean time I think a reverse lookup would be a not so dirty solution