Whenever I add .Where condition, my resultSet is always empty.
Below is my code:
QueryRequestOptions queryRequestOptions = new QueryRequestOptions()
{
PartitionKey = partitionKey
};
using (FeedIterator<Item> resultSet = container.GetItemLinqQueryable<Item>(requestOptions: queryRequestOptions)
.Where(x => x.IsContainer) // without this, I am able to return all the items
.ToFeedIterator())
{
while (resultSet.HasMoreResults)
{
foreach (var item in await resultSet.ReadNextAsync())
{
// print here
}
}
};
How can I apply filtering condition using Linq?
Related
Hi I want to set the value in the list of objects that matches the given condition in the where clause.Is it possible?
Other work around is to get the list of objects using where clause and then iterate using for Or foreach loop and update the value.
listOfRequestAssigned.Where(x => x.RequestedNumber == CurrentRequest);
I have list listOfRequestAssigned of objects and want to update some propery of the objects that match my search criteria.
class Request
{
bool _requestCompleted;
int _requestedNumber;
public int RequestedNumber
{
get { return _requestedNumber; }
set { _requestedNumber = value; }
}
public bool RequestCompleted
{
get { return _requestCompleted; }
set { _requestCompleted = value; }
}
}
I want to update RequestCompleted property of all objects that match criteria using Linq
You can use ForEach in Linq
listOfRequestAssigned.Where(x => x.RequestedNumber == CurrentRequest).ToList().ForEach(x => x.RequestCompleted = true);
if you have more than one update to do,
listOfRequestAssigned.Where(x => x.RequestedNumber == CurrentRequest).ToList().ForEach(x => { x.RequestCompleted = true; x.OtherProperty = value; } );
Where(...) give you a query, not a Request or a List<Request>. Use FirstOrDefault() if you want to have one (or 0) result, or ToList() if you want to have a list of results on wich you can use ForEach().
In general Linq is a query- not an update tool, but you can use a foreach:
var currentRequests = listOfRequestAssigned
.Where(x => x.RequestedNumber == CurrentRequest);
foreach(var req in currentRequests)
{
req.RequestCompleted = true;
}
Since you have specific collection of type List, you can just use ForEach and a conditional set:
listOfRequestAssigned.Foreach(x => { if (x.RequestedNumber == CurrentRequest) x.RequestCompleted = true;}});
If you had a more generic collection IEnumerable, you can use Select in Linq to build a projection where property will be set as desired (original collection will be left untouched!):
listOfRequestAssigned
.Where(x => x.RequestedNumber == CurrentRequest)
.Select(x => { x.RequestCompleted = true; return x; })
You can use to assign boolean value by following on comparing time. This is the very simplest and smart way for bool property.
listOfRequestAssigned.ForEach(x => x.RequestCompleted = x.RequestedNumber
== CurrentRequest);
I have 3 tables, team(id,name) player(id,teamid,name) playerdetail(id,playerid,height,weight), the relationship between team and player is one to many, the relationship between player and playerdetail is one to one.
I want to use eager loading to load all the information and print out the name of players who is higher than 2 meters.
I have write the code below,
using (var context = new TestEntities())
{
var query = from t in context.Teams.Include("Players.PlayerDetails") select t;
foreach (var v in query)
{
Console.WriteLine(v.Players.Any(x => x.PlayerDetails.Any(y => y.Height > 200)));
}
Console.Read();
}
It prints out only true and false, how can I modify it and make it print out the name of player?
Thanks in advance
Why don't you just query the players through context.Players like below?
using (var context = new TestEntities())
{
var query = context.Players.Include("Team").Include("PlayerDetails")
.Where(p => p.Height > 200);
foreach (var v in query)
{
Console.WriteLine(v.Name);
}
Console.Read();
}
I have a DataTable containing some data, and I am going to fetch some data from it using Linq to datatable.
The query looks like this:
var requiredData=dt.AsEnumerable()
.Where(row => row.Field<byte>("id") == 1)
.Select(x=> {
id = x.Field<int>("id"),
YYYYY = x.Field<string>("ColumnName2"),
ZZZZZ = x.Field<string>("ColumnName3")
}
);
Now, Please how do I iterate-through "requiredData"?
You could use a foreach loop:
foreach (var item in requiredData)
{
// TODO: use item.id, item.YYYYY and item.ZZZZZ here
}
I'm iterating the tables of a context and then the properties of those tables to eager load all columns in a context. I received some help via another question, but I don't seem to be able to figure out how to iterate the column properties of the actual table.
Final working code:
public static void DisableLazyLoading(this DataContext context)
{
DataLoadOptions options = new DataLoadOptions();
var contextTables = context.GetType().GetProperties().Where(n => n.PropertyType.Name == "Table`1");
foreach (var contextTable in contextTables)
{
var tableType = contextTable.GetValue(context, null).GetType().GetGenericArguments()[0];
var tableProperties = tableType.GetProperties().Where(n => n.PropertyType.Name != "EntitySet`1");
foreach (var tableProperty in tableProperties)
{
ParameterExpression paramExp = Expression.Parameter(tableType, "s");
Expression expr = Expression.Property(paramExp, tableProperty.Name);
options.LoadWith(Expression.Lambda(expr, paramExp));
}
}
context.LoadOptions = options;
}
You're only getting the ProperInfos. You need to get the values from the PropertyInfos:
var tablePropertInfos = context.GetType().GetProperties().Where(
n => n.PropertyType.Name == "Table`1");
foreach (var tablePropertyInfo in tablePropertInfos)
{
// Get the actual table
var table = tablePropertyInfo.GetValue(context, null);
// Do the same for the actual table properties
}
Once you have the PropertyInfo class, you need to get the value using the GetValue method.
I'm building a word anagram program that uses a database which contains one simple table:
Words
---------------------
varchar(15) alphagram
varchar(15) anagram
(other fields omitted for brevity)
An alphagram is the letters of a word arranged in alphabetical order. For example, the alphagram for OVERFLOW would be EFLOORVW. Every Alphagram in my database has one or more Anagrams. Here's a sample data dump of my table:
Alphagram Anagram
EINORST NORITES
EINORST OESTRIN
EINORST ORIENTS
EINORST STONIER
ADEINRT ANTIRED
ADEINRT DETRAIN
ADEINRT TRAINED
I'm trying to build a LINQ query that would return a list of Alphagrams along with their associated Anagrams. Is this possible?
UPDATE: Here's my solution based on the suggestions below! Thanks all!
using (LexiconEntities ctx = new LexiconEntities())
{
var words = ctx.words;
var query =
from word in words
where word.alphagram == "AEINRST"
group word by word.alphagram into alphagramGroup
select new { Alphagram = alphagramGroup.Key, Anagrams = alphagramGroup };
foreach (var alphagramGroup in query)
{
Console.WriteLine("Alphagram: {0}", alphagramGroup.Alphagram);
foreach (var anagram in alphagramGroup.Anagrams)
{
Console.WriteLine("Anagram: {0}", anagram.word1);
}
}
}
var list = anagrams.Select(
a => new {
Alphagram = a.ToCharArray().OrderBy(s => s).ToString(),
Anagram = a
}).toList();
A totally new answer...
You seem to need a groupby query look at How to: Group Data (Entity Framework).
this should accomplish what you want...
I did a testy with LINQ and this works...
var words = new List<Word>()
{
new ConsoleApplication1.Word("EINORST", "NORITES"),
new ConsoleApplication1.Word("EINORST", "OESTRIN"),
new ConsoleApplication1.Word("EINORST", "STONIER"),
new ConsoleApplication1.Word("ADEINRT", "ANTIRED"),
new ConsoleApplication1.Word("ADEINRT", "DETRAIN"),
new ConsoleApplication1.Word("ADEINRT", "TRAINED")
};
var q = words.GroupBy(w => w.Alphagram).Select(w => new { Alphagram = w.Key, Anagrams = w.Select(p => p.Anagram).ToList() }).ToList();
foreach (var item in q)
{
Console.WriteLine("Alphagram : {0}, Anagrams = {1}", item.Alphagram, String.Join(",", item.Anagrams));
}
var words = new List<Words>()
{
new Words("EINORST", "NORITES"),
new Words("EINORST", "OESTRIN"),
new Words("EINORST", "STONIER"),
new Words("ADEINRT", "ANTIRED"),
new Words("ADEINRT", "DETRAIN"),
new Words("ADEINRT", "TRAINED")
};
var result = words.GroupBy(w => w.Alphagram, w => w.Anagram)
.Select(w => new {
Alphagram = w.Key,
Anagrams = w.Where(p => w.Key.ToCharArray().SequenceEqualUnOrdered(p.ToCharArray())).ToList()
}
)
.ToList();
public static bool SequenceEqualUnOrdered<T>(this IEnumerable<T> first, IEnumerable<T> second)
{
return new HashSet<T>(first).SetEquals(second);
}
Is it what you are looking for? It is LINQ to Objects. You may want to use LINQ-to-SQL or LINQ-to-Entites to fetch your records into your objects and then use the above-mentioned LINQ-to-Objects query over the already-fetched object collection.