Passing array of functions in c#

Question

I want to create column validator where I can pass custom functions/methods.

Edit: I don't need to dynamically build these functions it is possible to build solution before hand, and I am constrained to .net 3.5. Basically I'm trying to create reusable class for my SSIS Script processes.

I did not know how to do that in C# so I created a fast representation in JavaScript of what I want to achieve here

// Data extracted from file
var data = "2|User2|15\r\n3|User1|13";

// Define columns in file
var columnKeys = ["ID", "Username", "Age"];

// Custome column validation
var columnValidation = {
    "ID": function (value) {
        if (isNaN(value)) return false;
        else return true;
    },
    "Username": function (value) {
        return true;
    },
    "Age": function (value) {
        return true;
    }
};

var ValidateColumns = function (data, keys, rules) {
    var rowSep = "\r\n";
    var colSep = "|";

    // Get rows
    var rows = data.split(rowSep);
    _.each(rows, function (row) {
        // Get columns
        var columns = row.split(colSep);

        // Validate columns
        _.each(columns, function (column) {
            if (rules[keys[columns.indexOf(column)]](column)) {
                console.log("Column " + keys[columns.indexOf(column)] + ": Passed");
            }
            else {
                console.log("Column " + keys[columns.indexOf(column)] + ": Failed");
            }
        });
    });
};

ValidateColumns(data, columnKeys, columnValidation);

Questions:

1. How to create functions/methods that will go in?
2. How to pass these functions inside class/method that will validate columns?

Answer 1

You should read about the Func and Actions

If you function return something (like a bool!) and/or uses multiple parameters, you should use Func<TReturn,TParam1,TParam2>[] and use as many TParam as you have parameters. There is alot of functionnality behind these so I recommend you to read about it. This link seems good : Explanation of Func

If your functions do not take any parameters and return void (which is not the case in your example, sorry), you could use a Action[] which is used like this :

Action action = () => //your function's code;
//Lame example of using Action[]
YourMethodThatTakesFuncAsParams(new Action[]{action,action,action});

If all of your functions return something different and/or uses different parameters, I don't think there is a clean solution to achieve this.

Little edit (since I can't comment on stuff!) I think Ben's answer is the most appropriate and direct approach to your problem

Answer 2

What you are looking for is a predicate. Essentially it represents a function with a definable input type and a boolean output.

Here is an example of passing an array of Predicates.

//this is a Predicate<string> b/c it takes a string as input and outputs a boolean
bool ExamplePredicate(string input)
{
    return input == "something";
}

//function accepting an array of Predicate<string> as input
bool Validate(Predicate<string>[] validators /*, other data input*/ )
{
    //use the array of validators to process your data.
}

void Test()
{
    //array of validators
    var validators = new Predicate<string>[]
    {
        aString => !string.IsNullOrEmpty(aString), // you can use lambda expressions
        ExamplePredicate               // or reference functions matching the predicate definitions
    }
    Validate(validators);
}

Documentation: http://msdn.microsoft.com/en-us/library/bfcke1bz(v=vs.110).aspx

Answer 3

You are looking for delegates. Please read the MSDN documentation. I can advise you these particular links:

http://msdn.microsoft.com/en-us/library/aa288459%28v=vs.71%29.aspx

http://msdn.microsoft.com/en-us/library/ms173172.aspx

The first is a tutorial about delegates and the second is about using them.