Create a list with methods with a return value C# and optional argument C#

Question

I have a list with methods that I am calling from a loop like below (with the help of a previous question: Create a list with methods with a return value C#):

string method;

var methods = new List<(Func<string> analysismethod, string caption)>
{
    (definitearticle, "Definite article"),
    (indefinitearticle, "Indefinite article"),
};
for (int i = 0; i < methods.Count(); i++)
{
    string gender = methods[i].analysismethod.Invoke();
    if (gender != "Cannot determine")
    {
        method = methods[i].caption;
        break;
    }
}

What I want to do now is to add an optional argument (a string) to each of the methods in methods (so I can reuse them for other purposes as well) like in:

definitearticle (word = default)
{
}

However, when I try add the optional argument, I get these errors:

Error   CS1950  The best overloaded Add method 'List<(Func<string> analysismethod, string caption)>.Add((Func<string> analysismethod, string caption))' for the collection initializer has some invalid arguments
Error   CS1503  Argument 1: cannot convert from '(method group, string)' to '(Func<string> analysismethod, string caption)'

How can I solve this?

edit: The reason why I want to use them with a specified string sometimes is that I sometimes want to analyse them for a specific input, whereas I sometimes just want to check for a default position in a sentence that I store in a struct:

public string indefinitearticle(string word = default)
{       
    if (word == default) 
    {
        word = AnalysisData.wordBeforeNoun;
    }

    string gender = default;
    if (word == "eine")
    {
        gender = "Fem";
    }
    else if (word == "ein")
    {
        gender = "Non fem";
    }
    
    return string.IsNullOrEmpty(gender) ? "Cannot determine" : gender;
}

Delegates should be for a single purpose. If the code you posted doesn't need the string, don't add it to those methods, use a new list of delegates with a different signature for the other purpose. — madreflection, Jan 29 '22 at 21:03
Regarding the error message... parameter defaults are not part of the method signature. If the method has the parameter, any delegate pointing to it must have a matching signature as if you removed the default from the method. — madreflection, Jan 29 '22 at 21:04
Use overloads instead of optional parameter (that actually what compile will do - generate corresponding overload methods) - than you can use both overloads for different purposes. `definitearticle() => definitearticle("default")` — Fabio, Jan 29 '22 at 21:06
That is, the problem would be solved if I have the same optional arguments to all of the methods? That would be a nice solutions since I intend to do just that once I am finished with the first one. — KGB91, Jan 29 '22 at 21:06
@Fabio That would be a solution, but I do not want to do that either since I want to be able to reuse the same analysis methods just sometimes with some user defined words. — KGB91, Jan 29 '22 at 21:07
No, it would not be solved by that because delegates signatures don't consider parameter defaults. — madreflection, Jan 29 '22 at 21:08

Fabio · Accepted Answer · 2022-01-29T21:14:44.600

2

Introduce overload methods

public string DefiniteArticle(string param1, string param2)  
{
    // calculate and return "some string";
}

public string DefiniteArticle()
{
    return DefiniteArticle("default value1", "default value2");
}

Now with parameterless overload you are able to add it to the collection of Func<string> to satisfy it's type and use "original" method for other purposes.

var delagates = new Func<string>[] { DefiniteArticle }

Notice that delegate are types as any other int or string - for being able to add method to the collection of delegates method should be same type. Overload method allows us to "decorate" original method with the required delegate type

edited Jan 29 '22 at 21:14

answered Jan 29 '22 at 21:10

Fabio

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Overloads will help to create an overload method which will satisfy delegate type. – Fabio Jan 29 '22 at 21:13
Yes, but I want the calculations to be exactly the same - I just want to be able to change the input if I am not going for the default case. – KGB91 Jan 29 '22 at 21:14
1

@KGB91, overload methods doing exactly what you are trying to achieve _change the input if I am not going for the default case_ – Fabio Jan 29 '22 at 21:15
Yes, but then I will have to do have the calculations duplicated since the only thing I want to do is to have another input, the calculations will be exactly the same. – KGB91 Jan 29 '22 at 21:24
1

What you mean by "duplicated calculation", calculation will exists in one method and will be called by overload. – Fabio Jan 29 '22 at 22:13
Ah, I see... I call the function with the calculations if I do not want specify an argument. That is indeed a creative workaround. – KGB91 Jan 29 '22 at 22:25

Create a list with methods with a return value C# and optional argument C#

1 Answers1