Tagged Questions
4
votes
2answers
59 views
How to write a dynamic Lambda Expression to access Nth Parent entity?
I have an application using nhibernate and linq to do my queries on database. Everything works fine but I have the follow model mapped (with auto-related):
public class A
{
public virtual int Id ...
1
vote
4answers
60 views
how to validate if lambda query returns null
I retrieve data from database with lambda like
var obj = DBContext.MyTable.Where(x => x.ID == 2).SingleOrDefault().MyColumn;
Actually , in MyTable , there is no ID with 2 .
So I got this ...
10
votes
1answer
254 views
C# Replace all elements of List<string> with the same pattern with LINQ
I have a C# List with thousands of strings:
"2324343"
"6572332"
"45122" ...
I would like to replace all of them with brackets around them, so then they would look like
"(2324343)"
"(6572332)"
...
1
vote
1answer
41 views
How to put a lambda with external parameters into a callback function
I have the following code which basically does what I want:
string firstName = "Chuck";
string lastName = "Norris";
filtered = dvds.Where(
dvd => (dvd.Element("Actors") != null) ...
2
votes
1answer
46 views
ICollection <T> to string array (using string property)
I have an ICollection of Thing. Thing has a string property Name. I would like to get an array of all Name in my ICollection. I know I can do this by iterating over the collection and building the ...
2
votes
2answers
46 views
lambda inner join and select all
Here is how I inner join in lambda ,
var myObject = tableNames.Join(tableSchool, x => x.sID , s => s.schoolID ,
( (x,s) => new { } ) ).ToList();
I have many fields in both tableNames ...
9
votes
2answers
143 views
What's the story with ExpressionType.Assign?
I was under the impression that assignment was not possible inside a lambda expression. E.g., the following (admittedly not very useful) code
Expression<Action<int, int>> expr = (x, y) ...
3
votes
3answers
118 views
Difficulty understanding particular lambda expression
This is a really simple question, I would imagine, for someone who knows lambda well. I am just now learning it and have run across one expression that doesn't make sense to me.
From what I ...
1
vote
4answers
75 views
LINQ List.AsParallel with boolean return
I've got a static List<long> primes of all known primes up to a certain point, and a function like this:
static bool isPrime(long p)
{
double rootP = Math.Sqrt(p);
foreach (long q in ...
4
votes
1answer
154 views
LINQ Expression Tree Any() inside Where()
I'm trying to generate the following LINQ query:
//Query the database for all AdAccountAlerts that haven't had notifications sent out
//Then get the entity (AdAccount) the alert pertains to, and find ...
3
votes
6answers
85 views
How to use a lambda expression as a parameter?
I have below method:
private List<TSource> Sort<TSource, TKey>(
List<TSource> list,
Func<TSource, TKey> sorter,
SortDirection direction)
{
...
}
and ...
0
votes
1answer
45 views
How to use linq to entities queries or Lists in linq to sql queries
I have a generic EF repository and need to get items from database using nested where statements.
var categoryGroups = repository.Categories.Where(a => a.Vehicles.Where(v =>
...
2
votes
3answers
64 views
Linq query to group items and query from the top item in each group
So, I have a list that looks something like this. Its basically a state history for a bunch of items, with the most recent state representing the current state.
Record Id State Date
...
-6
votes
3answers
71 views
Grouping objects in c# [closed]
I have a problem . I have some objects structured in the way described below:
InvoiceItem {
name = "Laptop"
price = 100$;
taxRate = 23% <-- can be 22% 8% etc;
quantity = 1;
}
Invoice {
...
2
votes
2answers
61 views
Dynamic number of evaluations on a where (lambda)
I'm new to Entity Framework, LINQ and lambda expressions. I need to do a search over a user's table, and I need to emulate one that already exists on a desktop application. This search gives only 1 ...
0
votes
1answer
69 views
Dynamic expression for filter IQueryable
I have a situation where I have just the property name (string) and the value by which desire filter.
I need to filter the list to return true if any name repeated.
Remembering that the filter should ...
1
vote
1answer
44 views
Check null result before accessing property or calling method
I would like to know if there is a better way or general rule to check null result before accessing property or calling method in C# Linq or lambda expressions. Thanks in advance.
At my ...
0
votes
1answer
24 views
Linq Query with Join not working on .Net 3.5 but works on .Net 4+
My query was working in .Net 3.5 SP1 until I added a join. The join was put in place to allow selection from the Comments entity even when there was no associated User entity. I get the following ...
0
votes
1answer
31 views
How to write lambda (linq) expression for sql?
I have an Sql statement for which I need go generate corresponding Lambda Expression (Linq).
Here is the SQL
Declare @CurrentUserId as int
Declare @CurrentDate as datetime
Set @CurrentDate = ...
0
votes
2answers
94 views
Where clause not entering lambda [closed]
I have the following lambda
var entities = JTransformer.Queryer.GetList()
.Where(x => { var y = JStubs.GetType(x.Name);
return (y.Impliments(baseType) && y.IsGenericType); });
...
2
votes
4answers
57 views
String building with particular pattern using char separator
I want to have an string in this format
name1,date1|name2,date2
For that I have written a method
int ifirstStringLength = strFirstStringArray.Length;
int iSecondStringLength = ...
2
votes
5answers
81 views
Lambda property value selector as parameter
I have a requirement to modify a method so that it has an extra parameter that will take a lambda expression that will be used on an internal object to return the value of the given property. Forgive ...
6
votes
4answers
100 views
Returning Expression<> using various class properties
I have something like this:
public Expression<Func<Message, bool>> FilterData()
{
switch (this.operatorEnum)
{
case FilterParameterOperatorEnum.EqualTo:
return ...
-5
votes
3answers
139 views
Could C# Linq do combinatorics?
I have this data structure:
class Product
{
public string Name { get; set; }
public int Count { get; set; }
}
var list = new List<Product>(){ { Name = "Book", Count = 40}, { Name = ...
0
votes
2answers
58 views
Expression.Equal - How to Compare Nullable and Non Nullable fields?
I have a nullable datetime field and I have to convert the string date field to a nullable datetime type (using Expression)....I did this using the below.
...
0
votes
1answer
28 views
Generating lambda expression - Type conversion Error
I have a generic method that filters a list of entities, filtering is done by generating lambda expressions:
protected object initFilters<TEntity>(string targetEntity, List<SearchItem> ...
0
votes
1answer
28 views
Will there be any performance or quality issues if we use lambda expression in foreach loop?
I have a piece of code as below -
var serviceResponseItems = new List<ServiceResponseItems>();
foreach (var item in serviceResponse.SomeItems.Where(x => !string.IsNullOrEmpty(x.Id) ...
2
votes
1answer
48 views
Runtime creation of LINQ expression
Say I have this expression:
int setsize = 20;
Expression<Func<Foo, bool>> predicate = x => x.Seed % setsize == 1
|| x.Seed % setsize == 4;
...
2
votes
5answers
78 views
Remove items from list<a> AND list<b> when a.Foo == b.Bar
I'm looking for an elegant way of comparing 2 different List<> collections and removing the items in which a specific field value matches. For example:
Customer object
class Customer
{
...
0
votes
3answers
74 views
How to query records based on date
I have a DataTable with 5 columns with type of int, string and DateTime. I have written a LINQ query to filter records by date. How do I get records by today and yesterday?
var Data = ...
