Function with variable arguments as parameter to another function

Question

How can I define a function that expects another function that returns a bool in c#?

To clarify, this is what I'd like to do using C++:

void Execute(boost::function<int(void)> fctn)
{
    if(fctn() != 0)
    {
        show_error();
    }
}

int doSomething(int);
int doSomethingElse(int, string);

int main(int argc, char *argv[])
{
    Execute(boost::bind(&doSomething, 12));
    Execute(boost::bind(&doSomethingElse, 12, "Hello"));
}

In my example above the Execute function in combination is with the bind gets the expected result.

Background:

I've got a bunch of functions, each returning a int but with different parameter count that are surrounded by the same error checking code. A huge code duplication I want to avoid...

Ian · Accepted Answer · 2014-02-27 14:14:10Z

1

You can probably achieve what you want by using Func. For example

void Execute(Func<bool> myFunc)
{
   if(myFunc() == false)
   {
      // Show error
   }
}

You can then define your Func either as a method, or a lambda:

// Define a method
private bool MethodFunc() {}

// Pass in the method
Execute(MethodFunc)

// Pass in the Lambda
Execute(() => { return true; });

You don't nececssairly need to pass the parameters in as you can now access them from the caller's scope:

Execute(() => { return myBool; });
Execute(() => { return String.IsNullOrEmpty(myStr); });

edited Feb 27, 2014 at 14:14

answered Feb 27, 2014 at 13:34

Ian

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2 Comments

Ronald McBean Over a year ago

A Func<bool> is a function that returns bool without parameters, i.e. the same as a C++ Func<bool(void)> ?

Ian Over a year ago

But you can now access them via the calling lambda - so you don't explicitly need to define them on the method signature.

Only a Curious Mind · Accepted Answer · 2014-02-27 13:44:56Z

1

With my solution, you can perform any function, any input parameter, with any return, this is a very generic implementation

Example:

public T YourMethod<T>(Func<T> functionParam)
{
   return functionParam.Invoke();
}

public bool YourFunction(string foo, string bar, int intTest)
{
    return true;
}

Call like This specifying the return :

YourMethod<bool>(() => YourFunction("bar", "foo", 1));

Or like this:

YourMethod(() => YourFunction("bar", "foo", 1));

edited Feb 27, 2014 at 13:44

answered Feb 27, 2014 at 13:38

Only a Curious Mind

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2 Comments

Ronald McBean Over a year ago

Why do you use Invoke to call the function, instead of calling it directly?

Only a Curious Mind Over a year ago

its more easy if you need to pass parameters

TYY · Accepted Answer · 2014-02-27 13:44:03Z

0

  without argument  do this 

  void Execute(Func<bool> fctn)
    {
        if(fctn() )
        {
            show_error();
        }
    }  

  with arguments you can do something like this:

    void Execute<T>(Func<T[],bool> fctn)
    {
        var v = new T[4];
        if(fctn(v) )
        {
            show_error();
        }
    }

edited Feb 27, 2014 at 13:44

answered Feb 27, 2014 at 13:37

TYY

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1 Comment

Ronald McBean Over a year ago

How do I use that with a function that has parameters (the bind part)?

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