Develop Reference

c# LiveCharts WPF how to add 0 value to a date where data does not exist to show in CartesianChart

This question is propably more a concept question, but I'm stuck here logically.
I'm using LiveChart for WPF and I try to build a simple CartesianChart dynamically.
I load my Data from a CSV into a List, I'm counting how many times each datapair is in that file and add the amount. The result from this Linq request looks like this:
[0] { Dates = "20191123", Rank = "1st", Amount = 1 } <Anonymous Type>
I go through this result to pick me each date individually for the Lables of my CartesianChart
Now I would like to add my result Data into the CartesianChart for that I need a SeriesCollection mine looks like this:
SeriesCollection = new SeriesCollection
{
new LineSeries
{
Title = "1st",
Values = new ChartValues<int> {}
},
new LineSeries
{
Title = "2nd",
Values = new ChartValues<int> {}
},
new LineSeries
{
Title = "3rd",
Values = new ChartValues<int> {}
}
}
But when I go through my data on some dates I dont have for example first place, so I need a 0 amount value for this day. I'm struggeling to add this to my data.
Here is pretty much the whole code block im experimenting with, that also why it looks a little messy.
var data = File.ReadAllLines(FilePathes.resultPath).ToList();
var rankHistoryList = new List<RankHistory>();
foreach (var line in data)
{
rankHistoryList.Add(RankHistory.parse(line));
};
var result = rankHistoryList.GroupBy(x => new { x.Dates, x.Rank })
.Select(g => new { g.Key.Dates, g.Key.Rank, Amount = g.Count() })
.ToList();
var dates = new List<string>();
foreach (var entry in result)
{
dates.Add(entry.Dates);
}
var singleDates = dates.GroupBy(x => x).Select(grp => grp.First()).ToArray();
foreach (var day in singleDates) {
foreach (var entry in result) {
if (entry.Rank == "1st" && day == entry.Dates)
{
SeriesCollection[0].Values.Add(entry.Amount);
}
else if (entry.Rank != "1st" && day == entry.Dates)
{ SeriesCollection[0].Values.Add(0); }
}
}

I think my answer is the most complicated but at least it works:
var allRanks = new List<string>
{
"1st"
,"2nd"
,"3rd"
};
foreach (var entry in result)
{
dates.Add(entry.Dates);
}
var singleDates = dates.GroupBy(x => x).Select(grp => grp.First()).ToArray();
Labels = singleDates;
foreach (var ran in allRanks)
{
foreach (var day in singleDates)
{
if (ran == "1st")
{
if (result.Exists(x => x.Dates == day && x.Rank == ran) == true)
{
SeriesCollection[0].Values.Add(result.Where(w => w.Dates == day && w.Rank == ran).Select(x => x.Amount).First());
}
else SeriesCollection[0].Values.Add(0);
}
if (ran == "2nd")
{
if (result.Exists(x => x.Dates == day && x.Rank == ran) == true)
{
SeriesCollection[1].Values.Add(result.Where(w => w.Dates == day && w.Rank == ran).Select(x => x.Amount).First());
}
else SeriesCollection[1].Values.Add(0);
}
if (ran == "3rd")
{
if (result.Exists(x => x.Dates == day && x.Rank == ran) == true)
{
SeriesCollection[2].Values.Add(result.Where(w => w.Dates == day && w.Rank == ran).Select(x => x.Amount).First());
}
else SeriesCollection[2].Values.Add(0);
}
}
}

Remove list in list

I have a list that stores an instance of the list. I want to remove the object from the sublist with IdName == "149"
List<Product> productList = new List<Product>()
{
new Product()
{
Id = 1,
Model = "Phone",
TypeProd = new CheckTypes() { ChTypes = new List<CHType> { new CHType() { Id = 8, IdName = "261"}, new CHType () {Id = 9 , IdName = "149" } } }
},
new Product()
{
Id = 1,
Model = "Printer",
TypeProd = new CheckTypes() { ChTypes = new List<CHType> { new CHType() { Id = 8, IdName = null}, new CHType () {Id = 8 , IdName = "261" } } }
}
};
var pr = productList.Select(s => s.TypeProd).Where(w => w.ChTypes.Any(a => a.IdName != null && a.IdName.Contains("149"))).ToList();
// I
var pr0 = pr.Select(s => s.ChTypes).Where(w => w.Any(a => a.Id == 9)).ToList();
// II
var pr1 = pr.Select(s => s.ChTypes).Except(pr0);
// III
pr.Select(s=>s.ChTypes).ToList().RemoveAll(a => a.Any(item => item.IdName.Contains("149")));
foreach (var item in pr)
{
foreach (var item2 in item.ChTypes)
{
Console.WriteLine(item2.IdName);
}
Console.WriteLine("End");
}
Console.ReadKey();
I get to delete the whole sequence, but how to delete one element from the sequence?

Use Remove() to remove a given item, or use RemoveAt() to remove the item at a given location.

I think, you are complicating it more than it needs to be. You simply need to loop over all the ChTypes List and remove the unwanted ChType. It can be easily accomplished by the below code
foreach (var chType in productList.Select(prod => prod.TypeProd.ChTypes))
chType.RemoveAll(c => c.IdName != null && c.IdName.Contains("149"));
All your LINQ lines for pr, pr0, pr1 and pr.Select().ToList().RemoveAll() are all unnecessary. Also, in your current code you are picking up only CHType with Id = 9, not sure if that is by mistake or your code is correct but your question missed specifying it.
Since the OP insists on avoiding foreach below is a a bad LINQ way of doing it
productList.Select(prod => prod.TypeProd.ChTypes)
.Select(chType => chType.RemoveAll(c => c.IdName != null && c.IdName.Contains("149")))
.ToList();

Use linq to match up pairs of rows in a set

In the system I use modifications to data are received in pairs of rows old and new with a RowMod flag, for example deleted, added, updated and unchanged rows come through as:
RowID Data RowMod
Row1 "fish" ""
Row1 "fish" "D"
Row2 "cat" "A"
Row3 "fox" ""
Row3 "dog" "U"
Row4 "mouse" ""
I'd like to match these up using the RowID that each row has and get something like:
RowID OldData NewData RowMod
Row1 "fish" null "D"
Row2 null "cat" "A"
Row3 "fox" "dog" "U"
Row4 "mouse" "mouse" ""

class Program
{
static void Main(string[] args)
{
IEnumerable<DataRow> rows = new[]
{
new DataRow(1,"fish",""),
new DataRow(1,"fish","D"),
new DataRow(2,"cat","A"),
new DataRow(3,"fox",""),
new DataRow(3,"dog","U"),
new DataRow(4,"mouse","")
};
var result = rows
.GroupBy(x => x.Id)
.Select(g => new
{
Count = g.Count(),
Id = g.First().Id,
FirstRow = g.First(),
LastRow = g.Last()
}).Select(item => new
{
RowId = item.Id,
OldData = item.Count == 1 && item.FirstRow.RowMod != "" ? null : item.FirstRow.Data,
NewData = item.LastRow.RowMod == "D" ? null : item.LastRow.Data,
RowMod = item.LastRow.RowMod
});
//Or using query syntax
var result2 = from x in rows
orderby x.Id, x.RowMod
group x by x.Id into g
select new
{
RowId = g.First().Id,
OldData = g.Count() == 1 && g.First().RowMod != "" ? null : g.First().Data,
NewData = g.Last().RowMod == "D" ? null : g.Last().Data,
RowMod = g.Last().RowMod
};
// Test
Console.WriteLine("RowID\tOldData\tNewData\tRowMod");
foreach (var item in result)
{
Console.WriteLine("{0}\t'{1}'\t'{2}'\t'{3}'",item.RowId,item.OldData ?? "null",item.NewData ?? "null",item.RowMod);
}
}
}
public class DataRow
{
public int Id { get; set; }
public string Data { get; set; }
public string RowMod { get; set; }
public DataRow(int id, string data, string rowMod)
{
Id = id;
Data = data;
RowMod = rowMod;
}
}
Output:
RowID OldData NewData RowMod
1 'fish' 'null' 'D'
2 'null' 'cat' 'A'
3 'fox' 'dog' 'U'
4 'mouse' 'mouse' ''

I am not sure if this is the best way to achieve your requirement but this is what I have:-
var result = rows.GroupBy(x => x.RowId)
.Select(x =>
{
var firstData = x.FirstOrDefault();
var secondData = x.Count() == 1 ? x.First().RowMod == "A" ? firstData : null
: x.Skip(1).FirstOrDefault();
return new
{
RowId = x.Key,
OldData = firstData.RowMod == "A" ? null : firstData.Data,
NewData = secondData != null ? secondData.Data : null,
RowMod = String.IsNullOrEmpty(firstData.RowMod) && secondData != null ?
secondData.RowMod : firstData.RowMod
};
});
Working Fiddle.

Getting the two parts of the intended object can be done iteratively:
foreach(var rowId in myList.Select(x => x.RowId).Distinct())
{
//get the left item
var leftItem = myList.SingleOrDefault(x => x.RowId == rowId && String.IsNullOrWhiteSpace(x.rowmod);
//get the right item
var rightItem = myList.SingleOrDefault(x => x.RowId == rowId && !String.IsNullOrWhiteSpace(x.rowmod);
}
Your question doesn't specify how you create the second object. Is it a different class?
Either way, you can extrapolate from the above snippet that either item might be null if it doesn't exist in the original set.
All you need to do is use those found objects to create your new object.

While I love LINQ a lot, I don't think it is appropriate here as you want to buffer some values while iterating. If you do this with LINQ, it will be at best not performing well, at worst it will iterate the collection multiple times. It also looks way cleaner this way in my opinion.
IEnumerable<TargetClass> MapOldValues(IEnumerable<SourceClass> source)
{
var buffer = new Dictionary<string, string>();
foreach(var item in source)
{
string oldValue;
buffer.TryGetValue(item.RowId, out oldValue);
yield return new TargetClass
{
RowId = item.RowId,
OldData = oldValue,
NewData = (item.RowMod == "D" ? null : item.Data),
RowMod = item.RowMod };
// if the rows come sorted by ID, you can clear old values from
// the buffer to save memory at this point:
// if(oldValue == null) { buffer.Clear(); }
buffer[item.RowId] = item.Data;
}
}
if you then only want the latest updates, you can go with LINQ:
var latestChanges = MapOldValues(source).GroupBy(x => x.RowId).Select(x => x.Last());

I guess there are more elegant ways to do it, but this produces the output you expect:
public class MyClass
{
public int RowID { get; set; }
public string Data { get; set; }
public string RowMod { get; set; }
}
var result = (from id in myList.Select(x => x.RowID).Distinct()
let oldData = myList.Where(x => x.RowID == id).SingleOrDefault(x => x.RowMod.Equals("")) != null
? myList.Where(x => x.RowID == id).Single(x => x.RowMod.Equals("")).Data
: null
let newData = myList.Where(x => x.RowID == id).SingleOrDefault(x => !x.RowMod.Equals("")) != null
? myList.Where(x => x.RowID == id).Single(x => !x.RowMod.Equals("")).Data
: null
let rowMod = myList.Where(x => x.RowID == id).SingleOrDefault(x => !x.RowMod.Equals("")) != null
? myList.Where(x => x.RowID == id).Single(x => !x.RowMod.Equals("")).RowMod
: null
select new
{
RowID = id,
OldData = oldData,
NewData = rowMod == null ? oldData : rowMod.Equals("D") ? null : newData,
RowMod = rowMod
});
foreach (var item in result)
{
Console.WriteLine("{0} {1} {2} {3}", item.RowID, item.OldData ?? "null", item.NewData ?? "null", item.RowMod ?? "-");
}

How to use local variables in a lambda expression

I have 2 list object of type of some class,
class person
{
public string id { get; set; }
public string name { get; set; }
}
List<person> pr = new List<person>();
pr.Add(new person { id = "2", name = "rezoan" });
pr.Add(new person { id = "5", name = "marman" });
pr.Add(new person { id = "3", name = "prithibi" });
List<person> tem = new List<person>();
tem.Add(new person { id = "1", name = "rezoan" });
tem.Add(new person { id = "2", name = "marman" });
tem.Add(new person { id = "1", name = "reja" });
tem.Add(new person { id = "3", name = "prithibi" });
tem.Add(new person { id = "3", name = "prithibi" });
Now i have to get all the ids from "pr" ListObject that has no entry or odd number of entries in the "tem" ListObejct. using lamda.
To do this i have used,
HashSet<string> inconsistantIDs = new HashSet<string>(pr.Select(p => p.id).Where(p => tem.FindAll(t => t.id == p).Count == 0 || tem.FindAll(t => t.id == p).Count % 2 != 0));
and it works fine.
but you can see from the code i have used tem.FindAll(t => t.id == p).Count twice to comapre with ==0 and %2!=0.
Is there any way to use tem.FindAll(t => t.id == p).Count once and
save it to a temporary variable and then compare this variable with
==0 and %2!=0.
More simply i just want to use it once for two condition here.

Use a statement lambda instead of an expression lambda
var inconsistantIDs = new HashSet<string>(
pr.Select(p => p.id).Where(p =>
{
var count = tem.FindAll(t => t.id == p).Count;
return count == 0 || count % 2 != 0;
}
));

Perhaps simply:
var query = pr.Where(p => { int c = tem.Count(p2 => p.id == p2.id); return c == 0 || c % 2 != 0; });
returns two persons:
2 "rezoan"
5 "marman"

Besides statement lambda you can use let clause:
HashSet<string> inconsistantIDs = new HashSet<string>(
from p in pr
let count = tem.FindAll(t => t.id == p).Count
where count == 0 || count % 2 != 0
select p.id
);

HashSet<string> inconsistantIDs = new HashSet<string>(
pr.Select(p => new { Id = p.id, Cnt = tem.FindAll(t => t.id == p.id).Count() })
.Where(p => p.Cnt == 0 || p.Cnt % 2 != 0)
.Select(p => p.Id);

On a side note, strictly performance wise, you would get better performance if you created a hash mapping of each ID to its count and then search it in a loop.
Right now you have a O(n*m) algorithm, which would be reduced to O(n+m):
// create a map (id -> count), O(m) operation
var dictionary = new Dictionary<string, int>();
foreach (var p in tem)
{
var counter = 0;
dictionary.TryGetValue(p.id, out counter);
counter++;
dictionary[p.id] = counter;
}
// search the map, O(n) operation
var results = new HashSet<string>();
foreach (var p in pr)
{
var counter = 0;
dictionary.TryGetValue(p.id, out counter);
if (counter == 0 || counter % 2 != 0)
results.Add(p.id);
}

Linq Conditional .Any() Select

How can I perform a conditional select on a column value, where I have a preference over which value is returned. If I can't find the top choice, I settle on the next, if available, and then if not the next, etc. As it looks right now, it would take 3 total queries. Is there a way to simplify this further?
var myResult = string.Empty;
if (myTable.Where(x => x.ColumnValue == "Three").Any())
{
myResult = "Three"; // Can also be some list.First().Select(x => x.ColumnValue) if that makes it easier;
}
else if (myTable.Where(x => x.ColumnValue == "One").Any())
{
myResult = "One";
}
else if (myTable.Where(x => x.ColumnValue == "Two").Any())
{
myResult = "Two";
}
else
{
myResult = "Four";
}

You could use a string[] for your preferences:
string[] prefs = new[]{ "One", "Two", "Three" };
string myResult = prefs.FirstOrDefault(p => myTable.Any(x => x.ColumnValue == p));
if(myResult == null) myResult = "Four";
Edit Enumerable.Join is a very efficient hash table method, it also needs only one query:
string myResult = prefs.Select((pref, index) => new { pref, index })
.Join(myTable, xPref => xPref.pref, x => x.ColumnValue, (xPref, x) => new { xPref, x })
.OrderBy(x => x.xPref.index)
.Select(x => x.x.ColumnValue)
.DefaultIfEmpty("Four")
.First();
Demo

I wrote an extension method that effectively mirrors Tim Schmelter's answer (was testing this when he posted his update. :-()
public static T PreferredFirst<T>(this IEnumerable<T> data, IEnumerable<T> queryValues, T whenNone)
{
var matched = from d in data
join v in queryValues.Select((value,idx) => new {value, idx}) on d equals v.value
orderby v.idx
select new { d, v.idx };
var found = matched.FirstOrDefault();
return found != null ? found.d : whenNone;
}
// usage:
myResult = myTable.Select(x => x.ColumnValue)
.PreferredFirst(new [] {"Three", "One", "Two"}, "Four");
I've written one that will quit a little more early:
public static T PreferredFirst<T>(this IEnumerable<T> data, IList<T> orderBy, T whenNone)
{
// probably should consider a copy of orderBy if it can vary during runtime
var minIndex = int.MaxValue;
foreach(var d in data)
{
var idx = orderBy.IndexOf(d);
if (idx == 0) return d; // best case; quit now
if (idx > 0 && idx < minIndex) minIndex = idx;
}
// return the best found or "whenNone"
return minIndex == int.MaxValue ? whenNone : orderBy[minIndex];
}

I use a weighted approach in SQL where I assign a weight to each conditional value. The solution would then be found by finding the highest or lowest weight depending on your ordering scheme.
Below would be the equivalent LINQ query. Note that in this example I am assigning a lower weight a higher priority:
void Main()
{
// Assume below list is your dataset
var myList =new List<dynamic>(new []{
new {ColumnKey=1, ColumnValue ="Two"},
new {ColumnKey=2, ColumnValue ="Nine"},
new {ColumnKey=3, ColumnValue ="One"},
new {ColumnKey=4, ColumnValue ="Eight"}});
var result = myList.Select(p => new
{
ColVal = p.ColumnValue,
OrderKey = p.ColumnValue == "Three" ? 1 :
p.ColumnValue == "One" ? 2 :
p.ColumnValue == "Two" ? 3 : 4
}).Where(i=> i.OrderKey != 4)
.OrderBy(i=>i.OrderKey)
.Select(i=> i.ColVal)
.FirstOrDefault();
Console.WriteLine(result ?? "Four");
}

How about something like this:
var results = myTable.GroupBy(x => x.ColumnValue).ToList();
if (results.Contains("Three")) {
myResult = "Three";
} else if (results.Contains("One")) {
myResult = "One";
} else if (results.Contains("Two")) {
myResult = "Two";
} else {
myResult = "Four";
}