Reusable Control

Question

I'm been wanting to create a user control, but before I do I need to know how to do a few things or even if its possible. I know it possible to pass a method to a function (Link). Is it possible to set a variable that is of function type? For example I have a user control where in one function I need to call GetData function. Each GetData routine is different so I was wondering if its possible to pass that function in from the aspx.cs page?

Your question is very broad and vague. I'm guessing the terms you're looking for are "delegate" and "event handler". Consider reading up on these then ask a more specific question. — Bob Kaufman, May 10 '12 at 22:23
Thanks Bob. I will look into that. If I can pass a function into a private variable in a user control. Then I would be good. Thanks again. — MindGame, May 10 '12 at 22:28

Olivier Jacot-Descombes · Accepted Answer · 2012-05-12T15:51:33.150

The .NET Framework Library defines handy generic delegates (or "function types" as you call it). Function delegates that have a return value

Func<Ret>
Func<Arg, Ret>
Func<Arg1, Arg2, Ret>
...

Function delegates that have no return value

Action<>
Action<Arg>
Action<Arg1, Arg2>
...

You can define a method that accepts a delegate like this

void DrawFunction(Func<double, double> function, double x0, double x1)
{
    const double step = 0.1;

    for (x = x0; x <= x1; x += step) {
        double y = function(x);
        DrawPointAt(x, y);
    }
}

You can call it by either passing it an appropriate method or with a lambda expression.

Using this declaration

public double Square(double x)
{
    return x*x;
}

You can do the call (note that the parentheses () are missing after Square since we do not want to call this method here)

DrawFunction(Square, 0.0, 10.0);

You get the same result with a lambda expression

DrawFunction(x => x*x, 0.0, 10.0);

Reusable Control

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