Question

I have three classes that inherit from a class because I want those objects to be treated as the base class:

public class Find 
{
}

public class StringFind : Find
public class DateFind : Find
public class LongFind : Find

ok then I create an array of ‘Find’ objects and I want to test if each object is of type StringFind , DateFind or LongFind so I created something as:

protected bool CompareUnion(params Find[] f)
{
    foreach (var searchL in f)
    {
        if (f is StringFind)
        {
            //do something
            var a = 3;
        }
    }

    return true;
}

why f cannot be of type StringFind if StringFind inherts from that class? I thought that visual studio was wrong but I never hit the breakpoint and I am actually creating an array of StringFind objects.

Answer 1

It’s just a typo. You need:

if (searchL is StringFind) { ... }

f is just the array of Find objects you passed in, so it will only satisfy f is Find[].

Usually when I see code like that, though, I start thinking of ways to avoid it. Rather than testing for a specific type and changing the behaviour, why not have a virtual method and tailor the behaviour by overriding the method in the derived classes?