Say i have a class that contains these items publicly accessible via properties:
class MyClass
{
int switch1; //0 or 1
int switch2; //0 or 1
int switch3; //0 or 1
}
This class represents switch states, and each time a switch state changes, i would like to add it to my transition list
I have a large sorted list that contains instances of this class and would like to use a query to capture only the entries in my list where the switch state for any switch changes.
Is this possible using a linq query?
try this:
Assuming your class looks like:
public class State
{
public int Id { get; set; }
public int Switch1 { get; set; }
public int Switch2 { get; set; }
public int Switch3 { get; set; }
public override bool Equals(object obj)
{
var other = obj as State;
if (other != null)
{
return Switch1 == other.Switch1 &&
Switch2 == other.Switch2 &&
Switch3 == other.Switch3;
}
return false;
}
}
I just added an Equals() to compare flags and my Id field is purely to demonstrate which items changed.
We can then craft a LINQ query like:
State previous = null;
var transitions = list.Where(s =>
{
bool result = !s.Equals(previous);
previous = s;
return result;
})
.ToList();
Not elegant, but it works, if you had this data set:
var list = new List<State>
{
new State { Id = 0, Switch1 = 0, Switch2 = 0, Switch3 = 0 },
new State { Id = 1, Switch1 = 0, Switch2 = 0, Switch3 = 0 },
new State { Id = 2, Switch1 = 1, Switch2 = 0, Switch3 = 0 },
new State { Id = 3, Switch1 = 0, Switch2 = 1, Switch3 = 0 },
new State { Id = 4, Switch1 = 0, Switch2 = 1, Switch3 = 0 },
new State { Id = 5, Switch1 = 0, Switch2 = 1, Switch3 = 0 },
new State { Id = 6, Switch1 = 1, Switch2 = 1, Switch3 = 0 },
new State { Id = 7, Switch1 = 0, Switch2 = 0, Switch3 = 1 },
new State { Id = 8, Switch1 = 0, Switch2 = 0, Switch3 = 1 },
new State { Id = 9, Switch1 = 0, Switch2 = 0, Switch3 = 0 },
};
And ran the query, the list would contain your state transitions at items: 0, 2, 3, 6, 7, 9
I would do as follow:
class MyClass
{
int ID; //needs for recognize the message
int switch1; //0 or 1
int switch2; //0 or 1
int switch3; //0 or 1
public int Pattern
{
get { return switch1 + switch2 << 1 + switch3 << 2; }
}
}
Then it must be declared a dictionary with the previous-state messages:
Dictionary<int, int> _prevStates;
each cell has for key the ID, and for value the "Pattern" of the message.
At this point, let's suppose that the new incoming message stream is a list of MyClass:
IEnumerable<MyClass> incoming = ...
var changed = from msg in incoming
where _prevStates.ContainsKey(msg.ID) //what to do?
where _prevStates[msg.ID].Pattern != msg.Pattern
select msg;
Finally, you must update the dictionary with the changed patterns.
Cheers
Related
I have data arranged in this order in sql.
Now, I want to order this list with both QuestionDataTypeId and DisplayOrder, but want this QuestionDataTypeId = 0 at last. so finally result will be like first row = 6 then 7 then 8 and then 1 to 5.
I want to achieve this with C# and linq.
What I have tried so far?
here is my code but it's not working.
var data = entity
.OrderByDescending(m => m.QuestionDataTypeId == 0)
.ThenBy(m => m.QuestionDataTypeId)
.ThenBy(m => m.DisplayOrder);
I have fixed this with merging 2 different variables sorted separately for QuestionDataTypeId = 0 and all other QuestionDataTypeId, but just want to know what will be the proper linq for this case in single line.
any help would be really appreciated. thanks!
Try replace QuestionDataTypeId where value = 0
.OrderBy(x=>x.QuestionDataTypeId==0?int.MaxValue:x.QuestionDataTypeId)
.ThenBy(t=>t.DisplayOrder)
You can write your own comparer for OrderBy
Sample data structure:
public record Table
{
public Table(int qdtId, int displayOrder, string text)
{
QuestionDataTypeId = qdtId;
DisplayOrder = displayOrder;
Text = text;
}
public int QuestionDataTypeId { get; set; }
public int DisplayOrder { get; set; }
public string Text { get; set; }
}
public class TableComparer : IComparer<Table>
{
public int Compare(Table? x, Table? y)
{
if(x.QuestionDataTypeId!= 0 && y.QuestionDataTypeId!=0 || x.QuestionDataTypeId == 0 && y.QuestionDataTypeId == 0)
{
return y.QuestionDataTypeId.CompareTo(x.QuestionDataTypeId);
}
return x.QuestionDataTypeId == 0 && y.QuestionDataTypeId != 0 ? int.MinValue : int.MaxValue;
}
}
Then in the code:
List<StringConcatBug.Table> list = new()
{
new(0, 1, "Comfortable"),
new(0, 2,"attainable"),
new(0, 3,"recent goal"),
new(0, 4,"comfortable"),
new(2, 2,"Last Name"),
new(3, 3,"Email"),
new(0, 5, "feeling"),
new(1, 1, "First Name"),
};
var ordered = list.OrderByDescending(t=>t,new TableComparer());
foreach(var v in ordered) { Console.WriteLine(v);}
Output
Table { QuestionDataTypeId = 1, DisplayOrder = 1, Text = First Name }
Table { QuestionDataTypeId = 2, DisplayOrder = 2, Text = Last Name }
Table { QuestionDataTypeId = 3, DisplayOrder = 3, Text = Email }
Table { QuestionDataTypeId = 0, DisplayOrder = 1, Text = Comfortable }
Table { QuestionDataTypeId = 0, DisplayOrder = 2, Text = attainable }
Table { QuestionDataTypeId = 0, DisplayOrder = 3, Text = recent goal }
Table { QuestionDataTypeId = 0, DisplayOrder = 4, Text = comfortable }
Table { QuestionDataTypeId = 0, DisplayOrder = 5, Text = feeling }
I usually use this algorithm
var mult=100000; // You can select a different number depending how many records of
// the same type you expecting; Numbers should not overlap
var data = entity
.OrderBy(m => (m.QuestionDataTypeId*mult + m.DisplayOrder))
.....
I want to group a list that includes integer List<int>.
List<CNode> cNodes
and the CNode is
public class CNode
{
public List<int> Elements;
// ...
}
I can group the cNodes like that
var groups = cNodes.GroupBy(node => node.Elements[0]);
foreach (var group in groups )
{
// ...
}
but as you see the groupping is depends the first element, I want to group it by all elements
For example if node.Elements.Count == 5 expected grouping result should be the same as for:
var groups = cNodes.GroupBy(node => new
{
A = node.Elements[0],
B = node.Elements[1],
C = node.Elements[2],
D = node.Elements[3],
E = node.Elements[4]
});
I couldn't find the solution.
Thanks.
You can use something like node.Take(5) with a proper IEqualityComparer like this:
using System;
using System.Collections.Generic;
using System.Linq;
namespace ConsoleApp
{
class Program
{
static void Main(string[] args)
{
var cNodes = new List<CNode>
{
new CNode{Elements = new List<int>{ 0, 0, 1, 1, 1 } },
new CNode{Elements = new List<int>{ 0, 0, 0, 1, 1 } },
new CNode{Elements = new List<int>{ 0, 1, 1, 0 } },
new CNode{Elements = new List<int>{ 0, 1, 1, 0, 0 } },
new CNode{Elements = new List<int>{ 0, 0, 0, 0 } },
new CNode{Elements = new List<int>{ 0, 0, 0, 0 } }
};
Console.WriteLine("\tGroup by 2:");
foreach (var group in cNodes.GroupByElements(2))
Console.WriteLine($"{string.Join("\n", group)}\n");
Console.WriteLine("\tGroup by 3:");
foreach (var group in cNodes.GroupByElements(3))
Console.WriteLine($"{string.Join("\n", group)}\n");
Console.WriteLine("\tGroup by all:");
foreach (var group in cNodes.GroupByElements())
Console.WriteLine($"{string.Join("\n", group)}\n");
}
}
static class CNodeExtensions
{
public static IEnumerable<IGrouping<IEnumerable<int>, CNode>> GroupByElements(this IEnumerable<CNode> nodes) =>
nodes.GroupByElements(nodes.Min(node => node.Elements.Count));
public static IEnumerable<IGrouping<IEnumerable<int>, CNode>> GroupByElements(this IEnumerable<CNode> nodes, int count) =>
nodes.GroupBy(node => node.Elements.Take(count), new SequenceCompare());
private class SequenceCompare : IEqualityComparer<IEnumerable<int>>
{
public bool Equals(IEnumerable<int> x, IEnumerable<int> y) => x.SequenceEqual(y);
public int GetHashCode(IEnumerable<int> obj)
{
unchecked
{
var hash = 17;
foreach (var i in obj)
hash = hash * 23 + i.GetHashCode();
return hash;
}
}
}
}
internal class CNode
{
public List<int> Elements;
public override string ToString() => string.Join(", ", Elements);
}
}
Output is:
Group by 2:
0, 0, 1, 1, 1
0, 0, 0, 1, 1
0, 0, 0, 0
0, 0, 0, 0
0, 1, 1, 0
0, 1, 1, 0, 0
Group by 3:
0, 0, 1, 1, 1
0, 0, 0, 1, 1
0, 0, 0, 0
0, 0, 0, 0
0, 1, 1, 0
0, 1, 1, 0, 0
Group by all:
0, 0, 1, 1, 1
0, 0, 0, 1, 1
0, 1, 1, 0
0, 1, 1, 0, 0
0, 0, 0, 0
0, 0, 0, 0
You wrote:
I want to group it by all elements
The solution given by Alex will only group by a limited number of elements. You said you want to group it by all elements, even if you have a CNode with 100 elements. Besides: his solution also crashes if property Elements of one of the CNodes equals null.
So let's create a solution that meets your requirement.
The return value will be a sequence of groups, where every group has a Key, which is a sequence of CNodes. All elements in the group are all source CNodes that have a property Elements equal to the Key.
With equal you mean SequenceEqual. So Elements[0] == Key[0] and Elements[1] == Key[1], etc.
And of course, you want to decide when Elements[0] equals Key[0]: do you want to compare by reference (same object)? or are two CNodes equal if they have the same property values? Or do you want to specify a IEqualityComparer<CNode>, so that you can see they are equal if they have the same Name or Id?
// overload without IEqualityComparer, calls the overload with IEqualityComparer:
IEnumerable<IGrouping<IEnumerable<Cnode>, CNode>> GroupBy(
this IEnumerable<CNode> cNodes)
{
return GroupBy(cNodes, null);
}
// overload with IEqualityComparer; use default CNode comparer if paramer equals null
IEnumerable<IGrouping<IEnumerable<Cnode>, CNode>> GroupBy(
this IEnumerable<CNode> cNodes,
IEqualityComparer<CNode> cNodeComparer)
{
// TODO: check cNodes != null
if (cNodeComparer == null) cNodeComparer = EqualityComparer<CNode>.Default;
CNodeSequenceComparer nodeSequenceComparer = new CNodeSequenceComparer()
{
CNodeComparer = cNodeComparer,
}
return sequenceComparer.GroupBy(nodeSequenceComparer);
}
You've noticed I've transferred my problem to a new EqualityComparer: this compare takes two sequences of CNodes and declares them equal if they SequenceEqual, using the provided IEqualityComparer<CNode>:
class CNodeSequenceComparer : IEqualityComparer<IEnumerable<CNode>>
{
public IEqualityComparer<CNode> CNodeComparer {get; set;}
public bool Equals(IEnumerable<CNode> x, IEnumerable<CNode> y)
{
// returns true if same sequence, using CNodeComparer
// TODO: implement
}
}
One of the things we have to keep in mind, is that your property Elements might have a value null (after all, you didn't specify that this isn't the case)
public bool Equals(IEnumerable<CNode> x, IEnumerable<CNode> y)
{
if (x == null) return y == null; // true if both null
if (y == null) return false; // false because x not null
// optimizations: true if x and y are same object; false if different types
if (Object.ReferenceEquals(x, y) return true;
if (x.GetType() != y.GetType()) return false;
return x.SequenceEquals(y, this.CNodeComparer);
}
How should i bind the values without using index no. as above, how can use forLoop here if possible. in query i gor 14 rows and 4 columns.
public class SLRInvestmentPrev
{
[DbCol("BOOK_VALUE")]
public double BOOK_VALUE { get; set; }
[DbCol("INSTRUMENT_ID")]
public int instrument_id { get; set; }
}
Public void Compute()
{
var slrinvestmentPrev = Database.BindList<SLRInvestmentPrev>(Transaction, #"Query here");
View["BOOK_VALUE_HTM0"] = slrinvestmentPrev[0].BOOK_VALUE;
View["BOOK_VALUE_HTM1"] = slrinvestmentPrev[1].BOOK_VALUE;
View["BOOK_VALUE_HTM2"] = slrinvestmentPrev[2].BOOK_VALUE;
View["BOOK_VALUE_HTM3"] = slrinvestmentPrev[3].BOOK_VALUE;
View["BOOK_VALUE_HFT1"] = slrinvestmentPrev[4].BOOK_VALUE;
View["BOOK_VALUE_HFT2"] = slrinvestmentPrev[5].BOOK_VALUE;
View["BOOK_VALUE_HFT3"] = slrinvestmentPrev[6].BOOK_VALUE;
View["BOOK_VALUE_HFT4"] = slrinvestmentPrev[7].BOOK_VALUE;
View["BOOK_VALUE_HFT5"] = slrinvestmentPrev[8].BOOK_VALUE;
View["BOOK_VALUE_AFS1"] = slrinvestmentPrev[9].BOOK_VALUE;
View["BOOK_VALUE_AFS2"] = slrinvestmentPrev[10].BOOK_VALUE;
View["BOOK_VALUE_AFS3"] = slrinvestmentPrev[11].BOOK_VALUE;
View["BOOK_VALUE_AFS4"] = slrinvestmentPrev[12].BOOK_VALUE;
View["BOOK_VALUE_AFS5"] = slrinvestmentPrev[13].BOOK_VALUE;
}
given your books are HTM0 to AFS5 you could do something like
List<String> booklist = new List<string>(new String[] { "BOOK_VALUE_HTM0", "BOOK_VALUE_HTM1", "BOOK_VALUE_HTM2",<.....> "BOOK_VALUE_AFS5" } ); // or populate from some other means
int index = 0;
foreach (String sbook in booklist)
{
View[sbook] = slrinvestmentPrev[index].BOOK_VALUE;
index++
}
how to bind that right side index values to different variables using
for loop or is there any way to make code short and being error free
if suppose to be rows no are less than hard coded index values?
So you need a way to bind your names to the indexes, one way it to use a Dictionary:
var nameIndexes = new Dictionary<int, string>()
{
{ 0, "BOOK_VALUE_HTM0" }, { 1, "BOOK_VALUE_HTM1" }, { 2, "BOOK_VALUE_HTM2" }, { 3, "BOOK_VALUE_HTM3" },
{ 4, "BOOK_VALUE_HFT1" }, { 5, "BOOK_VALUE_HFT2" }, { 6, "BOOK_VALUE_HFT3" }, { 7, "BOOK_VALUE_HFT4" }, { 8, "BOOK_VALUE_HFT5" },
{ 9, "BOOK_VALUE_AFS1" }, { 10, "BOOK_VALUE_AFS2" }, { 11, "BOOK_VALUE_AFS3" }, { 12, "BOOK_VALUE_AFS4" }, { 13, "BOOK_VALUE_AFS5" }
};
for(int i = 0; i < slrinvestmentPrev.Count; i++)
{
View[nameIndexes[i]] = slrinvestmentPrev[i].BOOK_VALUE;
}
If the index always starts with 0 and has no gaps you could also use a List<string> or string[].
i have these data:
class MyTableItem
{
public long id { get; set; }
public long listId { get; set; }
public long listFieldValue { get; set; }
public long parentId { get; set; }
}
and:
var myData = new MyTableItem[]
{
new MyTableItem { id = 1, listId = 1, listFieldValue = 100, parentId = 1 },
new MyTableItem { id = 2, listId = 2, listFieldValue = 130, parentId = 1 },
new MyTableItem { id = 3, listId = 3, listFieldValue = 170, parentId = 1 },
new MyTableItem { id = 4, listId = 4, listFieldValue = 170, parentId = 1 },
new MyTableItem { id = 5, listId = 1, listFieldValue = 100, parentId = 2 },
new MyTableItem { id = 6, listId = 2, listFieldValue = 130, parentId = 2 },
new MyTableItem { id = 7, listId = 3, listFieldValue = 170, parentId = 2 },
new MyTableItem { id = 8, listId = 4, listFieldValue = 270, parentId = 2 },
...(continue)
};
var myMatchConditions = new int?[][] //id, rangeTypeId(equal, more, less, between), from, to
{
new int?[] { 1, 1, 100, null },
new int?[] { 2, 2, 125, null },
new int?[] { 3, 3, null, 175 },
new int?[] { 4, 4, 130, 180 }
...(can continue more)
};
now i need to know which myData (groupBy parrentId) are matched by my conditions,
let me explain more:
I want to know which parrent Id has listFieldValue where:
1) (listId == 1)&&(listFieldValue == 100)
and
2) (listId == 2)&&(listFieldValue > 125)
and
3) (listId == 3)&&(listFieldValue < 175)
and
4) ((listId == 4)&&(listFieldValue > 130)&&(listFieldValue < 180))
it must return (1)parrentId.
There you go. Explanations are at the bottom:
IEnumurable<MyTableItem> temp = myData ;
for (int i = 0; i < myMatchConditions.GetLength(0); i++)
{
var conditionType = myMatchConditions[i,1];
if (conditionType == 1)
{
temp = temp.Where(_ => _listFieldValue == myMatchConditions[i,2]);
}
else
{
if (conditionType == 2 || conditionType == 4)
{
temp = temp.Where(_ => _listFieldValue > myMatchConditions[i,2]);
}
if (conditionType == 3 || conditionType == 4)
{
temp = temp.Where(_ => _listFieldValue < myMatchConditions[i,3]);
}
}
}
I'm using IEnumurable<MyTableItem> which means it's Linq and not Linq to entities. I chose that because your myData is not an EF table but a simple array.
I go through all the "rows" with a for, you can do that with a foreach, and I add the Where clauses to filter out more and more each time (The actual filtering will happen only when you use that temp list)
I add a condition based on the type in the second cell, and if the type is 4... I add both the 2 and 3 type rules... which makes a 4 type rule
I have a table
ID|VALUE
VALUE is an integer field with possible values between 0 and 4. How can I query the count of each value?
Ideally the result should be an array with 6 elements, one for the count of each value and the last one is the total number of rows.
This simple program does just that:
class Record
{
public int Id { get; set; }
public int Value { get; set; }
}
class Program
{
static void Main(string[] args)
{
List<Record> records = new List<Record>()
{
new Record() { Id = 1, Value = 0},
new Record() { Id = 2, Value = 1 },
new Record() { Id = 3, Value = 2 },
new Record() { Id = 4, Value = 3 },
new Record() { Id = 5, Value = 4 },
new Record() { Id = 6, Value = 2 },
new Record() { Id = 7, Value = 3 },
new Record() { Id = 8, Value = 1 },
new Record() { Id = 9, Value = 0 },
new Record() { Id = 10, Value = 4 }
};
var query = from r in records
group r by r.Value into g
select new {Count = g.Count(), Value = g.Key};
foreach (var v in query)
{
Console.WriteLine("Value = {0}, Count = {1}", v.Value, v.Count);
}
}
}
Output:
Value = 0, Count = 2
Value = 1, Count = 2
Value = 2, Count = 2
Value = 3, Count = 2
Value = 4, Count = 2
Slightly modified version to return an Array with only the count of values:
int[] valuesCounted = (from r in records
group r by r.Value
into g
select g.Count()).ToArray();
Adding the rows count in the end:
valuesCounted = valuesCounted.Concat(new[] { records.Count()}).ToArray();
Here is how you would get the number of rows for each value of VALUE, in order:
var counts =
from row in db.Table
group row by row.VALUE into rowsByValue
orderby rowsByValue.Key
select rowsByValue.Count();
To get the total number of rows in the table, you can add all of the counts together. You don't want the original sequence to be iterated twice, though; that would cause the query to be executed twice. Instead, you should make an intermediate list first:
var countsList = counts.ToList();
var countsWithTotal = countsList.Concat(new[] { countsList.Sum() });