Difference between Explicit conversions and safe cast in c#

Question

First one is working, while second shows an error, what is the difference? I read documentation, and didnt find anything about it, it not so crucial but want to know some features

public static string GetConcat2<T>(T q)
    {
        if(q.GetType() == typeof(A))
        {
            var z = q as A;
        }
        if (q.GetType() == typeof(A))
        {
            var z = (A)q;
        }
        return "!!!!";
    }
public interface CustomInteface
{
    string InterfaceProperty1 { get; set; }
    string InterfaceProperty2 { get; set; }
    string Concat();
}
public class A : CustomInteface
{
    public string InterfaceProperty1 { get; set; }
    public string InterfaceProperty2 { get; set; }
    public string Concat() {
        return InterfaceProperty1 + InterfaceProperty2;
    }
}

What is the error, where does it throw the error? Try to provide all of the information and code necessary to reproduce the issue, Include a [MCVE]. — TheLethalCoder, Apr 27 '17 at 10:23
@TheLethalCoder var z = (A)q; here's an error, it couldnt cast to type A — GodlikeRabbit, Apr 27 '17 at 10:24

score 2 · Accepted Answer · answered Apr 27 '17 at 10:31

2

The line var z = (A)q; is throwing an error this means that the object q is not of type A. The way you are trying to cast is a bit awkward as well you should use one of the following patterns:

as followed by null check:

var z = q as A;
if (z == null) { /*the cast failed*/ }

is followed by explicit cast
```
if (q is A)
{
    var z = (A)q;
}
```

Note the first pattern will return null if the cast fails and the second will throw an exception. This is why you only see the exception in the second case as the first is "silently" failing.

answered Apr 27 '17 at 10:31

TheLethalCoder

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as u can see, i'm checking generic type, so it must be correct type if (q.GetType() == typeof(A)) – GodlikeRabbit Apr 27 '17 at 10:35
@GodlikeRabbit Yes but don't do it that way, try doing it in the proper ways. Also debug your application and see what `q` actually is. – TheLethalCoder Apr 27 '17 at 10:40

Difference between Explicit conversions and safe cast in c#

1 Answers1