I have a string array of names or could be a List of names which can have multiple duplicate names. What I want to do is to get a list of top 5 most duplicate names. Could someone tell me what's the best way to do this?
Array[0] = 'Mike'
Array[1] = 'Tim'
Array[2] = 'Debra'
Array[3] = 'Mike'
Array[4] = 'Steve'
Array[5] = 'Mike'
Array[6] = 'Amy'
Array[7] = 'Tim'
Array[8] = 'Debra'
Array[9] = 'Amy'
Output: Mike has 3
Tim has 2
Debra has 2
Steve has 1
Amy has 1
Here is how it can be done with grouping:
var result = from name in namesArray
group name by name into g
orderby g.Count() descending
select new { Name = g.Key, Count = g.Count() };
If you need just top 5 - call .Take(5) of that:
var result = (from name in namesArray
group name by name into g
orderby g.Count() descending
select new { Name = g.Key, Count = g.Count() }).Take(5);
The easiest way to do this is to use GroupBy.
var result = Array
.GroupBy(x => x)
.Select(x => new { Name = x.Key; Count = x.Count() })
.OrderByDescending(x => x.Count)
.Take(5);
Looks to me like you want to do something with Linq,
var results = from name in names
group name by name into nameGroup
let count = nameGroup.Count()
orderby count descending
take 5
select new {Value = name, Count = count};
After which you can format the contents of the results as you desire.
Related
What could be the LINQ query for this SQL?
SELECT PartId, BSId,
COUNT(PartId), MAX(EffectiveDateUtc)
FROM PartCostConfig (NOLOCK)
GROUP BY PartId, BSId
HAVING COUNT(PartId) > 1
I am actually grouping by two columns and trying to retrieve max EffectiveDateUtc for each part.
This is what I could write. Stuck up on pulling the top record based on the date.
Also not sure, if this is a optimal one.
//Get all the parts which have more than ONE active record with the pat
//effective date and for the same BSId
var filters = (from p in configs
?.GroupBy(w => new
{
w.PartId,
w.BSId
})
?.Select(g => new
{
PartId = g.Key.PartId,
BSId = g.Key.BSId,
Count = g.Count()
})
?.Where(y => y.Count > 1)
select p)
?.Distinct()?.ToList();
var filteredData = (from p in configs
join f in filters on p.PartId equals f.PartId
select new Config
{
Id = p.Id,
PartId = p.PartId,
BSId = p.BSId,
//EffectiveDateUtc = MAX(??)
}).OrderByDescending(x => x.EffectiveDateUtc).GroupBy(g => new { g.PartId, g.BSId }).ToList();
NOTE: I need the top record (based on date) for each part. Was trying to see if I can avoid for loop.
The equivalent query would be:
var query =
from p in db.PartCostConfig
group p by new { p.PartId, p.BSId } into g
let count = g.Count()
where count > 1
select new
{
g.Key.PartId,
g.Key.BSId,
Count = count,
EffectiveDate = g.Max(x => x.EffectiveDateUtc),
};
If I understand well, you are trying to achieve something like this:
var query=configs.GroupBy(w => new{ w.PartId, w.BSId})
.Where(g=>g.Count()>1)
.Select(g=>new
{
g.Key.PartId,
g.Key.BSId,
Count = g.Count(),
EffectiveDate = g.Max(x => x.EffectiveDateUtc)
});
I need to get topic name and number of times (count) a given topic occurs.
Example:
Name: John
Topic: X, Y, Z => these are List<string>
Name: Bob
Topic: Y
Name: Suzy
Topic: Y, Z
Should generate output:
X: 1
Y: 3
Z: 2
I've tried this but it doesn't return correct result:
var result = from r in items
orderby r.Topic
group r by r.Topic
into grp
select new { key = grp.Key, cnt = grp.Count() };
You can flatten the contained collection with another from:
var result = from r in lineItems
from t in r.Topic // List<string>
group t by t into grp
orderby grp.Key
select new { key = grp.Key, cnt = grp.Count() };
I like to do this using SelectMany( to flatten the inner collection)
Just another way to do this
var result = items.SelectMany((w) => w.Topic)
.GroupBy((q) => q)
.Select((p) => new { Grp = p.Key, Cnt = p.Count() })
.OrderBy((g) => g.Cnt);
I have a list in my code that I need to filter through and return specific rows based on two criteria. The List in question is a list of models from a database. There are two ID properties on each model, one is the ID from the data table and is unique, the other is an ID we use to identify groups and can repeat. We'll call them ID and GroupID. Basically, I want the resulting list to have only one of each GroupID, and it should be the one with the highest (numerically speaking) ID. For example:
Input:
List<MyModel> modelList = new List<MyModel>
modelList[0].ID = 1 modelList[0].GroupID = 5
modelList[1].ID = 2 modelList[1].GroupID = 5
modelList[2].ID = 3 modelList[2].GroupID = 6
modelList[3].ID = 4 modelList[3].GroupID = 6
Desired Output:
Models at indexes 1 and 3.
Using LINQ:
var items = (from model in modelList
group model by model.GroupID into modelGroup
select modelGroup.Max(i => i.ID)).ToList();
What you have to do here is first order the modelList by ID and then GroupBy the list items by GroupID, then pull the item with max Id value.
var result = modelList.OrderByDescending(x => x.ID).GroupBy(x => x.GroupID).Select(x => x.First());
the above query will give you the result.
This is your solution:
var myData = models.GroupBy(model => model.GroupId)
.Select(group => group.OrderByDescending(model => model.Id).First());
Or you could also do this:
var myData = models.GroupBy(model => model.GroupId)
.Select(group => group.First(model => model.Id == group.Max(model1 => model1.Id)));
For fun, here's a fiddle.
You can try to use GroupBy.
var q = modelList.GroupBy(x => x.GroupID, x => x,
(key, g) => new {
GroupID = key,
Id = g.Max(c => c.ID)
});
This should group all your elements by GroupId and select Max ID in one of that groups.
Try this code:
List<MyModel> modelList = new List<MyModel>();
modelList.Add(new MyModel());
modelList.Add(new MyModel());
modelList.Add(new MyModel());
modelList.Add(new MyModel());
modelList[0].ID = 1; modelList[0].GroupID = 5;
modelList[1].ID = 2; modelList[1].GroupID = 5;
modelList[2].ID = 3; modelList[2].GroupID = 6;
modelList[3].ID = 4; modelList[3].GroupID = 6;
var list = from ml in modelList group ml by ml.ID into r select new { ID = r.Key, MaxGroupID = r.Max() };
this might help you
modelList.GroupBy(model => model.GroupId, g => g.Id).Select(item => item.Max())
var newModelList = modelList.GroupBy(ml => ml.GroupID)
.Select(g => new MyModel
{
ID = g.OrderByDescending(x => x.ID).First().ID,
GroupID = g.Key
}).ToList();
Details
1) GroupBy then Select to get distinct items over GroupID.
2) First() after OrderByDescending to get highest ID.
3) new MyModel in Select is just to be explicit about the projection.
I am trying to construct a LINQ query in C# that will give me a list of distinct values from a column in a dataset with a count for each row. The results would look like this.
State Count
AL 55
AK 40
AZ 2
Here is the SQL that does that.
SELECT name, COUNT(*) AS count
FROM architecture arch
GROUP BY name
ORDER BY name
I've figured out the LINQ to get the DISTINCT values which is.
var query = ds.Tables[0].AsEnumerable()
.OrderBy(dr1 => dr1.Field<string>("state"))
.Select(dr1 => new {state = dr1.Field<string>("state")})
.Distinct().ToList();
But I can't figure out how to get the COUNT(*) for each distinct value to work in LINQ. Any idea how I can add that into the LINQ query?
You need to group your results based on State and the Select count from the group like:
var query = ds.Tables[0].AsEnumerable()
.GroupBy(r => r.Field<string>("state"))
.Select(grp => new
{
state = grp.Key,
Count = grp.Count()
})
.OrderBy(o => o.state)
.ToList();
Group all rows by value of state column. Then order groups by grouping key. And last step - project each group into anonymous object with grouping key (state) and count of rows in group:
var query = ds.Tables[0].AsEnumerable()
.GroupBy(r => r.Field<string>("state"))
.OrderBy(g => g.Key)
.Select(g => new { State = g.Key, Count = g.Count() })
.ToList();
Query syntax will look like (I'll skip converting to list, to avoid mixing syntaxes):
var query = from r in ds.Tables[0].AsEnumerable()
group r by r.Field<string>("state") into g
orderby g.Key
select new {
State = g.Key,
Count = g.Count()
};
I think you need GroupBy
var query = ds.Tables[0].AsEnumerable()
.GroupBy(dr1 => dr1.Field<string>("state"))
.Select(g => new {state = g.Key, count = g.Count())
.ToList();
Why bother with Distinct, when you can translate your SQL query to LINQ almost word-for-word? You can do it like this:
var query = ds.Tables[0].AsEnumerable()
.GroupBy(dr1 => dr1.Field<string>("state"))
.Select(g => new {
State = g.Key
, Count = g.Count()
})
.OrderBy(p => p.State)
.ToList();
This produces a list of {State, Count} pairs. If you prefer a dictionary of state-to-count, you can change your query like this:
var query = ds.Tables[0].AsEnumerable()
.GroupBy(dr1 => dr1.Field<string>("state"))
.ToDictionary(g => g.Key, g => g.Count());
var query = ds.Tables[0].AsEnumerable()
.GroupBy(x=>x.Field<string>("state"))
.Select( g => new{
state = g.Key,
count = g.Count()
});
Guess what, the equivalent of group by is group by :)
var query = from dr1 in ds.Tables[0].AsEnumerable()
group dr1 by dr1.Field<string>("state") into state
select new { State = state.Key, Count = state.Count() };
var stat = from row in ds.Tables[0].AsEnumerable()
group row by new
{
Col1 = row["Name"],
} into TotalCount
select new
{
ActionName = TotalCount.Key.Col1,
ActionCount = TotalCount.Count(),
};
List<int> ListIdProducts = new List<int>();
var IdProductKey = from a in me.ProductKeywords where a.Keyword == item.Id select a;
foreach (var item2 in IdProductKey)
{
ListIdProducts.Add(item2.Product.Value);
}
Result is:
5
6
7
5
2
5
I need to get the following 5=3, 6=1, 7=1, 2=1
Use GroupBy LINQ method:
ListIdProducts
.GroupBy(i => i)
.Select(g => new { Value = g.Key, Count = g.Count() });
var query1 = from a in ListIdProducts
group a by new { a } into g
select new
{
item = g.Key,
itemcount = g.Count()
};
This a fairly standard group-by problem.
//untested
var IdProducts = from a in me.ProductKeywords
where a.Keyword == item.Id
group by a.Product.Value into g
select g.Count();