The following works in VB..
Dim q = allValues.GroupBy(Function(u) u.R).Select(Function(grp) grp).OrderByDescending(Function(a) a.Count).ToList
But not in C#..
dynamic q = allValues.GroupBy(u => u.R).Select(grp => grp).OrderByDescending(a => a.Count).ToList;
"allValues" is a list of color of various pixels. I'm trying to group the color R value and sort by the count descending to find the most used color.
I'm a noob to C# and Lambda. This is also my first post to the site. Thanks for any insite!
a.Count is a method, it needs parentheses -
.OrderByDescending(a => a.Count())
So does ToList() for that matter.
And a couple of little side issue:
Select(grp => grp) is pointless, you can just remove that bit.
The result does not need to be dynamic - you can just use var.
The right syntax is
var q = allValues // probably you mean "var" instead of "dynamic"
.GroupBy(u => u.R)
.Select(grp => grp) // that's redundant, you can remove it
.OrderByDescending(a => a.Count())
.ToList();
note () after Count and after ToList. "()" means that you call the method.
Related
SelectedStationCustomers
.SelectMany(customer => String.Format("{0}", customer.CustomerTelephone))
.ToList()
.ForEach(customer => client.SendMessage("12345678", NEED VALUE HERE, textMessage));
How do I get the value from customer.CustomerTelephone, into the ForEach statement? I have tried with customer.ToString(), but that does not seem to work.
You don't want to use SelectMany in this case. Just use Select.
And the String.Format does nothing for you in your example.
SelectedStationCustomers
.Select(customer => customer.CustomerTelephone)
.ToList()
.ForEach(customerTelephone => client.SendMessage("12345678", customerTelephone, textMessage));
I would use Select instead of SelectMany:
SelectedStationCustomers
.Select(customer => String.Format("{0}", customer.CustomerTelephone))
.ToList()
.ForEach(customer => client.SendMessage("12345678", customer, textMessage));
customer will hold the CustomerTelephone value
I'm trying to do a GroupBy and then OrderBy to a list I have. Here is my code so far:
reportList.GroupBy(x => x.Type).ToDictionary(y=>y.Key, z=>z.OrderBy(a=>a.Lost));
With the help of the last question I asked on linq I think the ToDictionary is probably unneeded, but without it I don't know how to access the inner value.
To be clear, I need to GroupBy the Type property and want the inner groups I get to be OrderBy the Lost property (an integer). I want to know if there is a better, more efficient way or at the least better then what I've done.
An explanation and not just an answer would be very much appreciated.
Yes, there is better approach. Do not use random names (x,y,z,a) for variables:
reportList.GroupBy(r => r.Type)
.ToDictionary(g => g.Key, g => g.OrderBy(r => r.Lost));
You can even use long names to make code more descriptive (depends on context in which you are creating query)
reportList.GroupBy(report => report.Type)
.ToDictionary(group => group.Key,
group => group.OrderBy(report => report.Lost));
Your code does basically the following things:
Group elements by type
Convert the GroupBy result into a dictionary where the values of the dictionary are IEnumerables coming from a call to OrderBy
As far as the code correctness it is perfectly fine IMO, but maybe can be improved in term of efficiency (even if depends on your needs).
In fact, with your code, the values of your dictionary are lazily evaluated each time you enumerate them, resulting in a call to OrderBy method.
Probably you could perform it once and store the result in this way:
var dict = reportList
.GroupBy(x => x.Type)
.ToDictionary(y => y.Key, z => z.OrderBy(a => a.Lost).ToList());
// note the ToList call
or in this way:
var dict = reportList.OrderBy(a => a.Lost)
.GroupBy(x => x.Type)
.ToDictionary(y => y.Key, z => z);
// here we order then we group,
// since GroupBy guarantees to preserve the original order
Looks fine to me. If you use an anonymous type instead of a Dictionary, you could probably improve the readability of the code that uses the results of this query.
reportList.GroupBy(r => r.Type)
.Select(g => new { Type = g.Key, Reports = g.OrderBy(r => r.Lost) });
I need to convert my city list into group by state and order by city within it.
I tried below one but not able to get it right. Would appreciate any help on this.
cities.GroupBy(g => g.state).Select(o => o.OrderBy(c => c.cityname));
Try below code
cities.GroupBy(g => g.state)
.Select(o =>new {
State = o.Key,
Cities = o.OrderBy(c => c.cityname).Tolist()})
.Tolist();
cits.OrderBy(d => d.cityname).GroupBy(d => d.state).SelectMany(g => g).ToList();
1 - Order by cityname first.
2 - Then group them according to state. Since you order first, groups are still ordered with respect to cityname property.
3 - Convert to single list. Otherwise, you will end up with list of groups.
Should work. I also advice using camel case notation for naming your variables.
The ToLookup function may give you what you need.
cities.ToLookup(c => c.state, c => c.city);
This will create an IGrouping<string, string> where you can iterate through the Key values (states) and operate on a set of city values.
To sort it first, just do cities.OrderBy(c => c.state).ThenBy(c => c.city).
Do the orderby first:
cities.OrderBy(c=>c.cityname).GroupBy (c => c.state);
You might want to order the states to so.
cities.OrderBy(c=>c.cityname).GroupBy (c => c.state).OrderBy (g => g.Key);
This is the query I am trying to do.
var commentActivity = project.ProjectDoc
.Select(c => c.Comment.Select(i => i.UserID))
.Distinct()
.Count();
What I want is the number of comments from distinct users on a specific project, but ANY ProjectDoc. This query "works" the result is just wrong. The model is like this, generically sketched.
Project
ProjectDoc
Comment
Update: I had to go one level deeper, based on the answer below I tried a few things that didn't work so I though I would post this as a reference. Note the two SelectMany methods.
var replyActivity = project.ProjectDoc
.SelectMany(c => c.Comment.SelectMany(r => r.CommentReply.Select(u => u.UserID)))
.Distinct()
.Count();
Use SelectMany instead of Select
project.ProjectDoc
.SelectMany(c => c.Comment.Select(i => i.UserID))
.Distinct()
.Count()
var data = (from con in project.ProjectDoc
select new
{
CommentCount=project.Comment.Count(x=>x.UserID==con.UserID)
}).ToList();
i think this will help you.
Why does this yield an empty set?
Object[] types = {23, 234, "hello", "test", true, 23};
var newTypes = types.Select(x => x.GetType().Name)
.Where(x => x.GetType().Name.Equals("Int32"))
.OrderBy(x => x);
newTypes.Dump();
When you do your select you're getting an IEnumerable<String>. Then you're taking the types of each string in the list (which is all "String") and filtering them out where they aren't equal to "Int32" (which is the entire list). Ergo...the list is empty.
Equals works just fine, it's your query that isn't correct. If you want to select the integers in the list use:
var newTypes = types.Where( x => x.GetType().Name.Equals("Int32") )
.OrderBy( x => x );
Reverse the order of the operations:
var newTypes = types.Where(x => x is int)
.OrderBy(x => x)
.Select(x => x.GetType().Name);
(Notice this also uses a direct type check instead of the rather peculiar .GetType().Name.Equals(…)).
The thing with LINQ is you've got to stop thinking in SQL terms. In SQL we think like this:-
SELECT Stuff
FROM StufF
WHERE Stuff
ORDER BY Stuff
That is what your code looks like. However in LINQ we need to think like this :-
FROM Stuff
WHERE Stuff
SELECT Stuff
ORDER BY Stuff
var newTypes = types.Select(x => x.GetType().Name)
.Where(x => x.Equals("Int32"))
.OrderBy(x => x);
This doesn't work because the Select statement will convert every value in the collection to the name of the underlying type of that value. The resulting collection will contain only string values and hence they won't ever have the name Int32.