Question

In some library I create I have to use following cast:

public void Foo(IList<uint> uintsList) // I need to use uint in the interface for this method
{
    List<double> doublesList = uintsList.Cast<double>().ToList();
    // Do something with the doublesList
}

I assumed that cast uint -> double should be always valid, and during my test it always worked fine.

But in the application, which uses this method the InvalidCastException occured. Unfortunately I do not have access to this application. So here are my questions:

• What could cause this exception occured? Isn’t the cast uint->double always valid?
• How can I secure my algorithm to avoid this exception?

EDIT
Of course, before casting I always perform check to avoid situation when uintsList is null or empty

EDIT 2
OK, the problem is solved, I changed the cast using the ConvertAll method, but still I don’t understand how it could happen?
So this question still bothers me: how the same part of the code could run properly at my computer, and throw an exception at another? Different compiler/environment versions? Some specific settings? Can anyone tell me where should I seek for the reasons of this situation to avoid it in the future?

Answer 1

See: C# Converting List<int> to List<double>

The cast uint -> double is valid, but you are casting a list of uints to a list of doubles. On most architectures the lists won’t even the same size (in bytes) – you will need to create an entirely new list and cast each element individually. I would use ConvertAll:

List<double> doublesList = uintsList.ConvertAll(x => (double)x);