Develop Reference

Linq select Objects from List which have empty String

is it possible in Linq to select from IEnumerable of this object
public class Foo
{
public int Id { get; set; }
public string Type { get; set; }
}
where Type is "" ?
if I loop over the list with that
foreach (Foo f in dataFoos)
{
Console.WriteLine(f.Id + f.Type);
}
it looks like
1one
2
3three
I have tried
var emptyType0 = dataFoos.Where(f => f.Type.Length <= 1);
var emptyType1 = dataFoos.Where(f => f.Type == null || f.Type == "");
both did not return any result. Any hint on how to properly check if String values are empty ?
if I do that
var df = dataFoos.Where(f => String.IsNullOrWhiteSpace(f.Type));
foreach (Foo f in df)
{
Console.WriteLine(f.Id + f.Type);
}
var df1 = dataFoos.Where(f => !String.IsNullOrWhiteSpace(f.Type));
foreach (Foo f in df1)
{
Console.WriteLine(f.Id + f.Type);
}
the second loop does not return any value
I am using dotnetcore c#. Thanks for any hint

This should cover almost every type of null/blank/just whitespace
var emptyType1 = foos.Where(f => String.IsNullOrWhiteSpace(f.Type));
but more likely what you want to do is exclude those - not include them
var dataFoos = foos.Where(f => !String.IsNullOrWhiteSpace(f.Type));
foreach (Foo f in dataFoos)
{
Console.WriteLine(f.Id + f.Type);
}

Get string from another string array if value matches

String Array 1: (In this format: <MENU>|<Not Served?>|<Alternate item served>)
Burger|True|Sandwich
Pizza|True|Hot Dog
String Array 2: (Contains Menu)
Burger
Pizza
Grill Chicken
Pasta
I need the menu is served or any alternate item served for that particular item.
Code:
for(int i = 0; i < strArr2.Length; i++)
{
if(strArr2.Any(_r => _r.Split('|').Any(_rS => _rS.Contains(strArr1[i]))))
{
var menu = strArr2[i];
var alternate = ? // need to get alternate item
}
}
As I commented in the code, how to get the alternate item in that string array? Please help, thanks in advance.
P.S: Any help to trim if condition is also gladly welcome.

Instead of any, you may use Where to get the value matching.
#Markus is having the detailed answer, I am just using your code to find a quick fix for you.
for(int i = 0; i < strArr2.Length; i++)
{
if(strArr2.Any(_r => _r.Split('|').Any(_rS => _rS.Contains(strArr1[i]))))
{
var menu = strArr2[i];
var alternate = strArr2.Where(_rs => _rs.Split('|').Any(_rS => _rS.Contains(strArr1[i]))).First().Split('|').Last();
}
}

In order to simplify your code, it is a good idea to better separate the tasks. For instance, it will be much easier to handle the contents of string array 1 after you have converted the contents into objects, e.g.
class NotServedMenu
{
public string Menu { get; set; }
public bool NotServed { get; set; }
public string AlternateMenu { get; set; }
}
Instead of having an array of strings, you can read the strings to a list first:
private IEnumerable<NotServedMenu> NotServedMenusFromStrings(IEnumerable<string> strings)
{
return (from x in strings select ParseNotServedMenuFromString(x)).ToArray();
}
private NotServedMenu ParseNotServedMenuFromString(string str)
{
var parts = str.Split('|');
// Validate
if (parts.Length != 3)
throw new ArgumentException(string.Format("Unable to parse \"{0}\" to an object of type {1}", str, typeof(NotServedMenu).FullName));
bool notServedVal;
if (!bool.TryParse(parts[1], out notServedVal))
throw new ArgumentException(string.Format("Unable to read bool value from \"{0}\" in string \"{1}\".", parts[1], str));
// Create object
return new NotServedMenu() { Menu = parts[0],
NotServed = notServedVal,
AlternateMenu = parts[2] };
}
Once you can use the objects, the subsequent code will be much cleaner to read:
var notServedMenusStr = new[]
{
"Burger|True|Sandwich",
"Pizza|True|Hot Dog"
};
var notServedMenus = NotServedMenusFromStrings(notServedMenusStr);
var menus = new[]
{
"Burger",
"Pizza",
"Grill Chicken",
"Pasta"
};
var alternateMenus = (from m in menus join n in notServedMenus on m equals n.Menu select n);
foreach(var m in alternateMenus)
Console.WriteLine("{0}, {1}, {2}", m.Menu, m.NotServed, m.AlternateMenu);
In this sample, I've used a Linq join to find the matching items.

You could do something like that
string[] strArr1 = { "Burger|True|Sandwich", "Pizza|True|Hot Dog" };
string[] strArr2 = { "Burger", "Pizza", "Grill Chicken", "Pasta" };
foreach (string str2 in strArr2)
{
string str1 = strArr1.FirstOrDefault(str => str.Contains(str2));
if (str1 != null)
{
string[] splited = str1.Split('|');
string first = splited[0];
bool condition = Convert.ToBoolean(splited[1]);
string second = splited[2];
}
}

Remove 'duplicates' from a list of pairings

Title could be misleading, so an example:
I have a class:
class Pair
{
Book Book1;
Book Book2;
}
I have a list of these:
var list = new List<Pair>();
list.Add(new Pair() {
Book1 = new Book() { Id = 123 },
Book2 = new Book() { Id = 456 }
});
list.Add(new Pair() {
Book1 = new Book() { Id = 456 },
Book2 = new Book() { Id = 123 }
});
Now, despite the fact the books are 'flipped', my system should treat these as duplicates.
I need a method to remove one of these 'duplicates' from the list (any one - so let's say the first to make it simple).
What I've Tried
var tempList = new List<Pair>();
tempList.AddRange(pairs);
foreach (var dup in pairs)
{
var toRemove = pairs.FirstOrDefault(o => o.Book1.Id == dup.Book2.Id
&& o.Book2.Id == dup.Book1.Id);
if (toRemove != null)
tempList.Remove(toRemove);
}
return tempList;
This returns no items (given the example above), as both Pair objects would satisfy the condition in the lambda, I only one to remove one though.
NOTE: This wouldn't happen if I just removed the element from the collection straight away (rather than from a temporary list) - but then I wouldn't be able to iterate over it without exceptions.

You can set up an IEqualityComparer<Pair> concrete class and pass that to the .Distinct() method:
class PairComparer : IEqualityComparer<Pair>
{
public bool Equals(Pair x, Pair y)
{
return (x.Book1.Id == y.Book1.Id && x.Book2.Id == y.Book2.Id)
|| (x.Book1.Id == y.Book2.Id && x.Book2.Id == y.Book1.Id);
}
public int GetHashCode(Pair obj)
{
return obj.Book1.Id.GetHashCode() ^ obj.Book2.Id.GetHashCode();
}
}
And then use it like so:
var distinctPairs = list.Distinct(new PairComparer());

The problem is that you are removing the both duplicates.
Try this:
var uniquePairs = list.ToLookup( p => Tuple.Create(Math.Min(p.Book1.Id, p.Book2.Id), Math.Max(p.Book1.Id, p.Book2.Id)) ).Select( g => g.First() ).ToList();

I would use the following
foreach (var dup in pairs)
{
var toRemove = pairs.FirstOrDefault(o => o.Book1.Id == dup.Book2.Id
&& o.Book2.Id == dup.Book1.Id
&& o.Book1.Id > o.Book2.Id);
if (toRemove != null)
tempList.Remove(toRemove);
}
This will specifically remove the duplicate that is "out of order". But this (and your original) will fail if the duplicate pairs have the books in the same order.
A better solution (since we're looping over ever pair anyways) would be to use a HashSet
var hashSet = new HashSet<Tuple<int,int>>();
foreach (var item in pairs)
{
var tuple = new Tuple<int,int>();
if (item.Book1.Id < item.Book2.Id)
{
tuple.Item1 = item.Book1.Id;
tuple.Item2 = item.Book2.Id;
}
else
{
tuple.Item1 = item.Book2.Id;
tuple.Item2 = item.Book1.Id;
}
if (hashSet.Contains(tuple))
{
tempList.Remove(dup);
}
else
{
hashSet.Add(tuple);
}
}

I've managed to find a solution, but it's one I'm not happy with. It seems too verbose for the job I'm trying to do. I'm now doing an additional check to see whether a duplicate has already been added to the list:
if(toRemove != null && tempList.Any(o => o.Book1.Id == toRemove.Book2.Id
&& o.Book2.Id == toRemove.Book1.Id))
tempList.Remove(toRemove);
I'm very much open to alternative suggestions.

Convert custom delimited string to List<myClass>?

How do I turn this:
string x = "key:value|key:value|key:value|key:value";
into this?
List<myClass> listObj;
myClass definition:
public class myClass
{
public string keyName { get; set; }
public string keyValue { get; set; }
}
There has to be a way to do it using LINQ or something :)
thanks in advance!
* NOTE *
I should add I know how to do this splitting it and looping through it, but there has to be a better way :)

This will require separate ToList() call, but I like query syntax for its declarative nature:
from s in x.Split('|')
let parts = s.Split(':')
select new myClass {
keyName = parts[0],
keyValue = parts[1]
}
Or you can use fluent syntax:
x.Split('|')
.Select(s => {
var parts = s.Split(':');
return new myClass {
keyName = parts[0],
keyValue = parts[1]
};
}).ToList()

Well, since you really wanted to avoid splitting and looping...
public List<MyClass> Parse(string base, string workingName, string workingValue,
bool processingName = true,
List<MyClass> workingList = null, int index = 0)
{
if (workingList == null)
workingList = new List<MyClass>();
if (index >= base.Length)
{
return workingList;
}
if (base[index] = '|')
{
workingList.Add(new MyClass { keyName = workingName, keyValue = workingValue });
return Parse(base, "", "", true, workingList, index + 1);
}
else if (base[index] = ':')
{
return Parse(base, workingName, "", false, workingList, index + 1);
}
else if (processingName)
{
return Parse(base, workingName + base[index], "", processingName, workingList, index + 1);
}
else
{
return Parse(base, workingName, workingValue + base[index], processingName, workingList, index + 1);
}
}
But please, for the love of whatever you hold dear, don't do anything even remotely resembling that (and yes, this is untested, hand-written code, so there are probably errors - just making a joke about avoiding things).

Do this if you prefer to use your custom class instead of Dictionary
var result = from y in x.Split('|')
let obj = y.Split(':')
select new myClass{keyName = obj[0], keyValue = obj[1]};
var list = result.ToList();

Searching a nested List<T>

I have this data structure:
class Conference
{
private List<List<string>>_orgs;
public List<List<string>> Orgs
{
set { _orgs = value; } get { return _orgs; }
}
}
Data in this collection:
List<string> sublist = new List<string>();
sublist.Add("university");
sublist.Add("organization");
List<List<string>> list = new List<List<string>>();
list.Add(sublist);
Then:
Conference c = new Conference();
c.Orgs = list;
I have collection of conference objects:
List<Conference> listConferences = new List<Conference>();
listConferences.Add(c);
I want search a string like "uni" and find collection of conference have orgs like "uni". How can I do this?

You can do this:
var selection = listConferences
.Where(x => x.Orgs.SelectMany(y => y).Any(y => y.Contains("uni")))
.ToList();
Note:
the trailing ToList() might not be necessary depending on your needs (e.g. if you iterate selection only once you can skip it).

Please use this code, below;
instead of third one, you may use your own conference list. you can now use similar to like keyword.
List<string> first = new List<string>();
first.Add("University");
first.Add("Standard");
List<List<string>> second = new List<List<string>>();
second.Add(first);
List<List<List<string>>> third = new List<List<List<string>>>();
third.Add(second);
var e = third.Find(delegate(List<List<string>> r)
{
bool isValid = false;
if(r.Count > 0)
{
foreach(List<string> s in r)
{
if(s.Count > 0 )
{
isValid = s.FindAll(delegate(string t){ return t.StartsWith("uni", StringComparison.OrdinalIgnoreCase);}).Count > 0;
}
}
}
return isValid;
});

Done, one more workout using linq. You should be feeling comfortable with this:
var univ = from p in c.Orgs
select p.FindAll(r => r.FindAll(s => s.StartsWith("univ", StringComparison.OrdinalIgnoreCase)));