Casting in C#

Question

Hi friends I want to know that In which scenario I should be using (int) Int32.Parse and Convert.ToInt32? are they same or not? I do notice in certain condition that i cannot cast directly using (int) and I have to use Convert.ToInt32. I am not that sure why i do that. Further I just need some confirmations from you all. Thank you.

Vulpes · Answer

You should use a cast (int) if : 1. You want to convert another numeric type to 'int' but there's no implicit conversion from that type to int. This generally means that the type could contain values which int does not contain and so the conversion may therefore fail or lose accuracy. 2. You have an object reference which contains a boxed int and you want to unbox it. When you assign an 'int' to an object variable a wrapper is created on the heap and the int is copied into it - a process known as 'boxing'. To unbox it you need to cast back to int. For example; double d = 3.8; int i = (int)d; // rounds down so loses accuracy Console.WriteLine(i); // 3 object o = 4; // boxes the int value '4' on the heap int j = (int)o; // unboxes it by copying it to the variable 'j' Console.WriteLine(j); // 4

Sam Hobbs · Answer

It is true that if a null string is passed to Convert then it will not throw an exception but if an invalid string is passed to Convert then it will throw an exception.

Sam Hobbs · Answer

You need to convert the data when it is a string and you need the number so you can do calculations with it. A string and a number look totally different to the computer. It is very easy to look at the declaration of an object; if it is a string and you need to do calculations then you must convert; casting is not enough. Usually it is better to use the Int32.TryParse Method so that if the text is not a valid number your program will not crash.

Satyapriya Nayak · Answer

Hi Amit The Convert.ToInt32(String IFormatProvider) underneath calls the Int32.Parse. So the only difference is that if a null string is passed to Convert it returns 0 whereas Int32.Parse throws an ArgumentNullException. Refer http://www.codeproject.com/KB/cs/AgileWare_Convert_Int32.aspx Thanks