This is a general question, but here is the specific case I'm looking for a solution to:
I have a Dictionary<int, List<string>>
I want to apply various predicates to. I want one method that can take care of multiple LINQ queries such as these:
from x in Dictionary
where x.Value.Contains("Test")
select x.Key
from x in Dictionary
where x.Value.Contains("Test2")
select x.Key
So I'm looking for a method like so:
public int GetResult(**WhatGoesHere** filter)
{
return from x in Dictionary.Where(filter)
select x.Key;
}
To be used like so:
int result;
result = GetResult(x => x.Value.Contains("Test"));
result = GetResult(x => x.Value.Contains("Test2"));
What is the proper syntax for WhatGoesHere?
Predicates can be passed as method parameters. In the example, we pass a predicate function as the second parameter to the eval method.
The predicate is a predefined functional interface in Java defined in the java. util. Function package. It helps with manageability of code, aids in unit-testing, and provides various handy functions.
Pass a Method as a Parameter by Using the lambda Function in Java. This is a simple example of lambda, where we are using it to iterate the ArrayList elements. Notice that we're passing the lambda function to the forEach() method of the Iterable interface. The ArrayList class implements the Iterable interface.
You can use Func<KeyValuePair<int, List<string>>, bool>
:
public int GetResult(Func<KeyValuePair<int, List<string>>, bool> filter)
{
return (from x in Dictionary
where filter(x)
select x.Key).FirstOrDefault();
}
Or alternatively: Predicate<KeyValuePair<int, List<string>>>
. I think Func
which was introduced in .NET 3.5 is preferred these days.
You are using x
to mean two different things in your final example and this will give a compile error. Try changing one of the x
s to something else:
x = GetResult(y => y.Value.Contains("Test1"));
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With