Func is a family of delegate types in the .Net framework.
Func is a family of delegate types in the .net framework. They are in the System namespace and can be used to represent a function that returns a value and has zero or more parameters.
Questions tagged [func]
1154 questions
13
votes
1 answer
Assign a method with default values to Func<> without those parameters?
I would like to be able to do the following:
Func tryMethodFunc = TryMethod;
Where TryMethod has a signature like:
bool TryMethod(int value, int value2 = 0, double value3 = 100.0)
I'm not opposed to breaking the method up into a curried…
Firestrand
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12
votes
2 answers
Cannot assign a delegate of one type to another even though signature matches
My morbid curiosity has me wondering why the following fails:
// declared somewhere
public delegate int BinaryOperation(int a, int b);
// ... in a method body
Func addThem = (x, y) => x + y;
BinaryOperation b1 = addThem; // doesn't…
Hobbes
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12
votes
5 answers
use Func<> (or Action<>) or create own delegate?
Which one is better in, say, parameter type in a method (not related to LINQ).
Apparently Func is better since it's simpler, more descriptive, and if everyone is using this everything will become compatible (good).
However I notice Microsoft uses…
Louis Rhys
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12
votes
4 answers
Encapsulating Action and Func?
I'm trying to make a design for some sort of IExecutable interface. I will not get into details, but the point is that I have several Actions that need to be executed from a base class. They may take different parameters (no big deal), and they…
Alpha
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12
votes
2 answers
How to invoke Expression> against a collection
I have an interface that defines a repository from the Repository pattern:
interface IRepository
{
List GetAllCustomers(Expression> expression);
}
I've implemented it against Entity Framework:
class…
mason
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12
votes
2 answers
Func delegate doesn't chain methods
Lets imagine simple delegate calls:
void Main()
{
Func tfunc = null;
tfunc += Add; // bind first method
tfunc += Sub; // bind second method
Console.WriteLine(tfunc(2, 2));
}
private string Add(int a, int b)
{
…
Dariusz
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11
votes
1 answer
Extracting Func<> from Expression<>
I wanna extract the Func<> from the following Expression :
Expression, IOrderedQueryable>> order = q => q.OrderByDescending(c=>c.FullName);
Func, IOrderedQueryable> orderFunc = ?
How can I…
Mohammad Dayyan
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11
votes
2 answers
Difference between Func<> with delegate and lambda expression
while deepening myself to more advanced features of C#, I came across some code, which I didn't exactly know the difference of. It's about these two lines:
Func giveLength = (text => text.Length);
and
Func giveLength =…
Memet Olsen
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10
votes
4 answers
python positional args and keyword args
I am reading the source codes of mercurial, and found such a func def in commands.py:
def import_(ui, repo, patch1=None, *patches, **opts):
...
in python, postional args must be put ahead of keyword args. But here, patch1 is a keyword argument,…
guoqiao
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10
votes
1 answer
How to moq a Func
Trying to unit test a class whose constructor takes in a Func. Not sure how to mock it using Moq.
public class FooBar
{
public FooBar(Func fooBarProxyFactory)
{
_fooBarProxyFactory = fooBarProxyFactory;
…
kenwarner
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10
votes
3 answers
Dictionary with Func as key
I am wondering if this is a sane choice of key for a dictionary? What I want to do is use an expression as the key in a dictionary, something like:
var map3 = new Dictionary, int>();
map3.Add((x) => x % 2 == 0, 1);
…
user380689
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10
votes
1 answer
How can I Create a Expression.Property of a child object
normally I create an expresion in this way.
ParameterExpression pe = Expression.Parameter(typeof(object1), "x");
string Name = "property1";
MemberExpression left = Expression.Property(pe, (object1).GetProperty(Name));
it produces left = x =>…
Diana G
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9
votes
1 answer
What does os.O_TRUNC do?
func OpenFile(name string, flag int, perm FileMode) (*File, error)
f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE|O_TRUNC, 0755)
Does "O_TRUNC" empty the entire file before writing?
What do they mean with "truncates"?
Also, does the…
user12316120
9
votes
2 answers
Func(Of Tin, Tout) using a lambda expression with ByRef argument gives incompatible signature error
Why does this:
Private [Function] As Func(Of Double, String) = Function(ByRef z As Double) z.ToString
gives the following error:
Nested function does not have a signature that is compatible with delegate String)'.
While this:
Private [Function]…
Brian Mulcahy
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9
votes
1 answer
Static method signature type arguments and partial application
I've been looking into Functional Programming lately and wanting to bring some concepts to my C# world. I'm trying to compose functions to create services (or whatever you'd call them) instead of creating classes with injectable dependencies.
I've…
Aage
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