For example, I have a list of excel cells
List<Cell> cells = new List<Cell>
{
new Cell("4"),
new Cell("Hez"),
new Cell("Method"),
new Cell("4"),
new Cell("Val"),
new Cell("Method"),
}
I need to get the only unique cell (in this case Cell("Val"), Cell("Hez")) so Distinct() is not for me.
I found this solution but it doesn't return any data at all
var uniqueTest = allData.GroupBy(cell => cell)
.Where(group => group.ToString().Count() == 1)
.Select(group => group.Key);
I think the problem is Cell object doesn't contain any comparison methods (This is IronXl lib) so this is why I'm using ToString() here.
But I don't quite understand linq yet, so any explanation or advice is appreciated
Remarks:
I need to get a list of cells back, but with unique values
Step 1: Group the cells by their value.
Step 2: Keep only the groups of size 1.
Step 3: Get the only item from each group.
var uniqueCells =
allData.GroupBy(cell => cell.Value) //Step 1
.Where(g => g.Count() == 1) //Step 2
.Select(g => g.Single()) //Step 3
This should be easy.
Lets count the value of Number 4 is Key.. then your linq should look like this
var uniqueTest = allData.GroupBy(x=> x.Key).Select(x=> x.First()).Select(x=> x.Key);
If I understand you correctly, and i'm not sure if I do, you can use .First() or the more robust .Single()
var uniqueTest = allData.First(c => c.ToString() == "Val");
In this sample i'm assuming c.ToString() will give you the cell's value. Otherwise it will likely be something like c.Value or something.
There are als the OrDefault variants.
Check out this article for the differences;
https://www.c-sharpcorner.com/blogs/singleordefault-vs-firstordefault-in-linq-query1
if you class Cell is something like this.
public class Cell
{
public Cell(string mystring)
{
MyString = mystring;
}
public string MyString { get; set; }
then this will work to get a unique list:
List<Cell> UniqueCells = new List<Cell>();
foreach (var cell in cells)
{
if(!UniqueCells.Any(c=>c.MyString == cell.MyString))
{
UniqueCells.Add(cell);
}
}
In this case only the first cell containing 'Method' and '4' will be added. the '!' and '.Any' are the essential parts.
Related
This is what I did so far:
class CardDisplayer
{
public int CardSuit;
public int CardValue;
}
List<CardDisplayer> _playerHand;
// Group all cards by the same suit
var _handDuplicates = _playerHand.GroupBy(x => x.CardSuit)
.Select(g => g.ToList())
.ToList();
CardDisplayer _duplicateFound = null;
// And then find all cards with the same value number
for (int i = 0; i < _handDuplicates.Count; i++)
{
var _handReference = _handDuplicates[i];
var _temp = _handReference.GroupBy(x => x.CardValue)
.Where(g => g.Count() > 1)
.Select(g => g.ToList())
.ToList();
// If you find more than one card with the same number
if(_temp.Count > 0)
{
// Take it
_duplicateFound = _temp.First().First();
break;
}
}
What I'm trying to achieve is after get the player's hand I want to find if the player has duplicates in his hand by looking if there is cards with the same suit and the same value.
I tried a lot of things on the internet but I cannot figure out how to get the list of duplicates using LINQ instead write all these lines of code.
Can someone know how to do it please?
Thank you.
you can use the GroupBy method to create a complex key, then use the Any method to find if at least on group has more then 1 object, or Where / FirstOrDefault to find the duplicates
var grouped = _handReference.GroupBy(g => new {suit=g.CardSuit, value=g.CardValue});
var hasDuplicates=grouped.Any(g=>g.Count()>1);
var duplicateList=grouped.Where(g=>g.Count()>1);
var duplicate=grouped.FirstOrDefault(g=>g.Count()>1);
After a while, I found the perfect solution based also on the answers.
// Get the reference for the player hand
List<List<CardDisplayer>> _playerHand = playersSlots[_playerIndex];
// Find in the player's hand duplicates
var _duplicates = _playerHand.GroupBy(x => new { x.CardSuit, x.CardValue })
.Where(x => x.Skip(1).Any())
.SelectMany(g => g)
.Distinct(new CardEqualityComparer()) // Use this only if you want unique results
.ToList();
var _duplicateCard = _duplicates.FirstOrDefault();
If you want unique results you can use a custom CardEqualityComparer class and use it with the Distinct of LINQ
/// <summary>
/// Used to compare if two cards are equals.
/// </summary>
class CardEqualityComparer : IEqualityComparer<CardDisplayer>
{
public bool Equals(CardDisplayer x, CardDisplayer y)
{
// Two items are equal if their keys are equal.
return x.CardSuit == y.CardSuit && x.CardValue == y.CardValue;
}
public int GetHashCode(CardDisplayer obj)
{
return obj.CardSuit.GetHashCode() ^ obj.CardValue.GetHashCode();
}
}
You can find the reference on the web: StackOverflow and DotNetPerls
Thank you, everyone, for the help.
How can I get the string from a list that best match with a base string using the Levenshtein Distance.
This is my code:
{
string basestring = "Coke 600ml";
List<string> liststr = new List<string>
{
"ccoca cola",
"cola",
"coca cola 1L",
"coca cola 600",
"Coke 600ml",
"coca cola 600ml",
};
Dictionary<string, int> resultset = new Dictionary<string, int>();
foreach(string test in liststr)
{
resultset.Add(test, Ldis.Compute(basestring, test));
}
int minimun = resultset.Min(c => c.Value);
var closest = resultset.Where(c => c.Value == minimun);
Textbox1.Text = closest.ToString();
}
In this example if I run the code I get 0 changes in string number 5 from the list, so how can I display in the TextBox the string itself?
for exemple : "Coke 600ml" Right now my TextBox just returns:
System.Linq.Enumerable+WhereEnumerableIterator`1
[System.Collections.Generic.KeyValuePair`2[System.String,System.Int32]]
Thanks.
Try this
var closest = resultset.First(c => c.Value == minimun);
Your existing code is trying to display a list of items in the textbox. I looks like it should just grab a single item where Value == min
resultset.Where() returns a list, you should use
var closest = resultset.First(c => c.Value == minimun);
to select a single result.
Then the closest is a KeyValuePair<string, int>, so you should use
Textbox1.Text = closest.Key;
to get the string. (You added the string as Key and changes count as Value to resultset earilier)
There is a good solution in code project
http://www.codeproject.com/Articles/36869/Fuzzy-Search
It can be very much simplified like so:
var res = liststr.Select(x => new {Str = x, Dist = Ldis.Compute(basestring, x)})
.OrderBy(x => x.Dist)
.Select(x => x.Str)
.ToArray();
This will order the list of strings from most similar to least similar.
To only get the most similar one, simply replace ToArray() with First().
Short explanation:
For every string in the list, it creates an anonymous type which contains the original string and it's distance, computed using the Ldis class. Then, it orders the collection by the distance and maps back to the original string, so as to lose the "extra" information calculated for the ordering.
I have a list stored in resultlist as follows:
var resultlist = results.ToList();
It looks something like this:
ID FirstName LastName
-- --------- --------
1 Bill Smith
2 John Wilson
3 Doug Berg
How do I remove ID 2 from the list?
List<T> has two methods you can use.
RemoveAt(int index) can be used if you know the index of the item. For example:
resultlist.RemoveAt(1);
Or you can use Remove(T item):
var itemToRemove = resultlist.Single(r => r.Id == 2);
resultList.Remove(itemToRemove);
When you are not sure the item really exists you can use SingleOrDefault. SingleOrDefault will return null if there is no item (Single will throw an exception when it can't find the item). Both will throw when there is a duplicate value (two items with the same id).
var itemToRemove = resultlist.SingleOrDefault(r => r.Id == 2);
if (itemToRemove != null)
resultList.Remove(itemToRemove);
Short answer:
Remove (from list results)
results.RemoveAll(r => r.ID == 2); will remove the item with ID 2 in results (in place).
Filter (without removing from original list results):
var filtered = result.Where(f => f.ID != 2); returns all items except the one with ID 2
Detailed answer:
I think .RemoveAll() is very flexible, because you can have a list of item IDs which you want to remove - please regard the following example.
If you have:
class myClass {
public int ID; public string FirstName; public string LastName;
}
and assigned some values to results as follows (used for all examples below):
var results = new List<myClass> {
new myClass { ID=1, FirstName="Bill", LastName="Smith" }, // results[0]
new myClass { ID=2, FirstName="John", LastName="Wilson" }, // results[1]
new myClass { ID=3, FirstName="Doug", LastName="Berg" }, // results[2]
new myClass { ID=4, FirstName="Bill", LastName="Wilson" } // results[3]
};
Then you can define a list of IDs to remove:
var removeList = new List<int>() { 2, 3 };
And simply use this to remove them:
results.RemoveAll(r => removeList.Any(a => a==r.ID));
It will remove the items 2 and 3 and keep the items 1 and 4 - as specified by the removeList. Note that this happens in place, so there is no additional assigment required.
Of course, you can also use it on single items like:
results.RemoveAll(r => r.ID==4);
where it will remove Bill with ID 4 in our example.
A last thing to mention is that lists have an indexer, that is, they can also be accessed like a dynamic array, i.e. results[3] will give you the 4th element in the results list (because the first element has the index 0, the 2nd has index 1 etc).
So if you want to remove all entries where the first name is the same as in the 4th element of the results list, you can simply do it this way:
results.RemoveAll(r => results[3].FirstName == r.FirstName);
Note that afterwards, only John and Doug will remain in the list, Bill is removed (the first and last element in the example). Important is that the list will shrink automatically, so it has only 2 elements left - and hence the largest allowed index after executing RemoveAll in this example is 1 (which is results.Count() - 1).
Some Trivia:You can use this knowledge and create a local function
void myRemove() { var last = results.Count() - 1;
results.RemoveAll(r => results[last].FirstName == r.FirstName); }
What do you think will happen, if you call this function twice?
Like
myRemove(); myRemove();
Answer (click to show):
The first call will remove Bill at the first and last position, the second call will remove Doug and only John Wilson remains in the list.
Note: Since C# Version 8, you can as well write results[^1] instead of var last = results.Count() - 1; and results[last]:
void myRemove() => results.RemoveAll(r => results[^1].FirstName == r.FirstName);
So you would not need the local variable last anymore (see indices and ranges). Furthermore, since it is a one-liner, you don't require the curly braces and can use => instead.
For a list of all the new features in C#, look here.
DotNetFiddle: Run the demo
resultList = results.Where(x=>x.Id != 2).ToList();
There's a little Linq helper I like that's easy to implement and can make queries with "where not" conditions a little easier to read:
public static IEnumerable<T> ExceptWhere<T>(this IEnumerable<T> source, Predicate<T> predicate)
{
return source.Where(x=>!predicate(x));
}
//usage in above situation
resultList = results.ExceptWhere(x=>x.Id == 2).ToList();
You don't specify what kind of list, but the generic List can use either the RemoveAt(index) method, or the Remove(obj) method:
// Remove(obj)
var item = resultList.Single(x => x.Id == 2);
resultList.Remove(item);
// RemoveAt(index)
resultList.RemoveAt(1);
More simplified:
resultList.Remove(resultList.Single(x => x.Id == 2));
there is no needing to create a new var object.
There is another approach. It uses List.FindIndex and List.RemoveAt.
While I would probably use the solution presented by KeithS (just the simple Where/ToList) this approach differs in that it mutates the original list object. This can be a good (or a bad) "feature" depending upon expectations.
In any case, the FindIndex (coupled with a guard) ensures the RemoveAt will be correct if there are gaps in the IDs or the ordering is wrong, etc, and using RemoveAt (vs Remove) avoids a second O(n) search through the list.
Here is a LINQPad snippet:
var list = new List<int> { 1, 3, 2 };
var index = list.FindIndex(i => i == 2); // like Where/Single
if (index >= 0) { // ensure item found
list.RemoveAt(index);
}
list.Dump(); // results -> 1, 3
Happy coding.
Try this code:
resultlist.Remove(resultlist.Find(x => x.ID == 2));
... or just resultlist.RemoveAt(1) if you know exactly the index.
{
class Program
{
public static List<Product> list;
static void Main(string[] args)
{
list = new List<Product>() { new Product() { ProductId=1, Name="Nike 12N0",Brand="Nike",Price=12000,Quantity=50},
new Product() { ProductId =2, Name = "Puma 560K", Brand = "Puma", Price = 120000, Quantity = 55 },
new Product() { ProductId=3, Name="WoodLand V2",Brand="WoodLand",Price=21020,Quantity=25},
new Product() { ProductId=4, Name="Adidas S52",Brand="Adidas",Price=20000,Quantity=35},
new Product() { ProductId=5, Name="Rebook SPEED2O",Brand="Rebook",Price=1200,Quantity=15}};
Console.WriteLine("Enter ProductID to remove");
int uno = Convert.ToInt32(Console.ReadLine());
var itemToRemove = list.Find(r => r.ProductId == uno);
if (itemToRemove != null)
list.Remove(itemToRemove);
Console.WriteLine($"{itemToRemove.ProductId}{itemToRemove.Name}{itemToRemove.Brand}{itemToRemove.Price}{ itemToRemove.Quantity}");
Console.WriteLine("------------sucessfully Removed---------------");
var query2 = from x in list select x;
foreach (var item in query2)
{
/*Console.WriteLine(item.ProductId+" "+item.Name+" "+item.Brand+" "+item.Price+" "+item.Quantity );*/
Console.WriteLine($"{item.ProductId}{item.Name}{item.Brand}{item.Price}{ item.Quantity}");
}
}
}
}
I have the following ItemArray:
dt.Rows[0].ItemArray.. //{0,1,2,3,4,5}
the headers are : item0,item1,item2 etc..
So far, to get a value from the ItemArray I used to call it by an index.
Is there any way to get the value within the ItemArray with a Linq expression based on the column name?
Thanks
You can also use the column-name to get the field value:
int item1 = row.Field<int>("Item1");
DataRow.Item Property(String)
DataRow.Field Method: Provides strongly-typed access
You could also use LINQ-to-DataSet:
int[] allItems = (from row in dt.AsEnumerable()
select row.Field<int>("Item1")).ToArray();
or in method syntax:
int[] allItems = dt.AsEnumerable().Select(r => r.Field<int>("Item1")).ToArray();
If you use the Item indexer rather than ItemArray, you can access items by column name, regardless of whether you use LINQ or not.
dt.Rows[0]["Column Name"]
Tim Schmelter's answer is probably what you are lookin for, just to add also this way using Convert class instead of DataRow.Field:
var q = (from row in dataTable.AsEnumerable() select Convert.ToInt16(row["COLUMN1"])).ToArray();
Here's what I've come up with today solving a similar problem. In my case:
(1)I needed to xtract the values from columns named Item1, Item2, ... of bool type.
(2) I needed to xtract the ordinal number of that ItemN that had a true value.
var itemValues = dataTable.Select().Select(
r => r.ItemArray.Where((c, i) =>
dataTable.Columns[i].ColumnName.StartsWith("Item") && c is bool)
.Select((v, i) => new { Index = i + 1, Value = v.ToString().ToBoolean() }))
.ToList();
if (itemValues.Any())
{
//int[] of indices for true values
var trueIndexArray = itemValues.First().Where(v => v.Value == true)
.Select(v => v.Index).ToArray();
}
forgot an essential part: I have a .ToBoolean() helper extension method to parse object values:
public static bool ToBoolean(this string s)
{
if (bool.TryParse(s, out bool result))
{
return result;
}
return false;
}
I have a DataTable. I can also use Linq.
In a DataTable have many columns, and rows. One of the column is called as feedCode. its type is string. in database it's length is 7 varchar, nullable.
feedCode may contain values as 9051245, 9051246, 9051247, 9031454, 9021447.
Method must return most matched (in this case starting with 905) value 905 (first 3 character of string)?
thanks.
Try to use this code:
var feedCodes = new string[] { "9051245", "9051246", "9051247", "9051245", "9031454", "9021447" };
var mostOccuring = feedCodes.Where(feedCode => feedCode != null)
.GroupBy(feedCode => feedCode.Length < 3 ? feedCode : feedCode.Substring(0, 3))
.OrderByDescending(group => group.Count())
.FirstOrDefault();
if(mostOccuring == null)
{
//some exception handling
}
else
{
//process mostoccuring.Key
}
this code also handle feedcodes with length less than 3 (even empty strings). If you don't want to use them just filter them out in where statement.
Maybe i didn't understand your question correctly but maybe this will be a starting point for your:
//The feedCodes (i put one in two times, to have one appearing most often)
var values = new string[] { "9051245", "9051246", "9051247", null, "", "9051245", "9031454", "9021447" };
//Just filter the list for filled up values
var query = values.Where(value => !String.IsNullOrEmpty(value))
//and group them by their starting text
.GroupBy(value => value.Substring(0, 3))
//order by the most occuring group first
.OrderByDescending(group => group.Count());
//Iterate over all groups or just take the first one with query.First() or query.FirstOrDefault()
foreach (var group in query)
{
Console.WriteLine(group.Key + " Count: " + group.Count());
}