Func Delegate

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Func Delegate

Ronald Rex 1,666

Hi Friends. I'm struggling with trying to understand this code below. Not sure why str is assingned to selector. Very confusing how this is written selector = str => str.ToUpper(); is selector the name of the delegate or is that a variable? Is str a method or variable? Please if I could get some help to understand this very confusing syntax. Does whats to the left of the => go to str.ToUpper();? And great articles on Delegates and Delegate Even Handlers?

// Declare a Func variable and assign a lambda expression to the
// variable. The method takes a string and converts it to uppercase.
Func<string, string> selector = str => str.ToUpper();

// Create an array of strings.
string[] words = { "orange", "apple", "Article", "elephant" };
// Query the array and select strings according to the selector method.
IEnumerable<String> aWords = words.Select(selector);

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Viorel 121.3K

I do not think that str is assigned to selector. The whole “str => str.ToUpper()” is assigned:

Func<string, string> selector = ( str => str.ToUpper() );

where “str => str.ToUpper()” is a short form of a function that looks like this:

string MyFunction( string str )
{
   return str.ToUpper();
}

Your anonymous compact form is added to selector.

Therefore, str is the name of function parameter.

To get the results, use something like this: string[] result = aWords.ToArray( ). Your function will be executed sequentially for all of items.

Ronald Rex 1,666 Reputation points

2023-08-14T16:58:37.55+00:00
Thanks that was very helpful. Are you saying that selector points to the function.... ?

string MyFunction( string str ) { return str.ToUpper(); }
Viorel 121.3K Reputation points

2023-08-14T17:30:34.7633333+00:00

In your example, we can say that the selector variable points to the function.

(But, in general, the selector is a list of functions. The lists has sense in case of events).
Ronald Rex 1,666 Reputation points

2023-08-14T18:31:00.1833333+00:00

selector is a list of functions? What does that mean?
Viorel 121.3K Reputation points

2023-08-14T18:43:42.5433333+00:00
It is possible to store more lambda functions, for example:

Func<string, string> selector = str => str.ToUpper( ); selector += str => str.ToLower(); selector += str => str + "ABC";

The words.Select(selector) will give the results returned by the third function. It has no sense to add the other two functions. Multiple functions are useful in other cases.
Ronald Rex 1,666 Reputation points

2023-08-14T19:12:48.0466667+00:00

Why can you only use results from third function. Give me an example where multiple functions are useful in other cases.
Ronald Rex 1,666 Reputation points

2023-08-14T19:38:27.0133333+00:00

Oh yeah events. I see what you are saying. I guess event chaining. But i really dont see the benefit of using a delegate just to make some strings in uppercase. I wish I understood some real power in using Delegates.

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Func Delegate

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