Can somebody clarify the C# is
keyword please. In particular these 2 questions:
Q1) line 5; Why does this return true?
Q2) line 7; Why no cast exception?
public void Test()
{
object intArray = new int[] { -100, -200 };
if (intArray is uint[]) //why does this return true?
{
uint[] uintArray = (uint[])intArray; //why no class cast exception?
for (int x = 0; x < uintArray.Length; x++)
{
Console.Out.WriteLine(uintArray[x]);
}
}
}
MSDN's description does not clarify the situation. It states that is
will return true if either of these conditions are met. (http://msdn.microsoft.com/en-us/library/scekt9xw(VS.71).aspx>MDSN Article)
expression is not null. expression can be cast to type.
I don't believe that you can do a valid cast of int[] into uint[]. Because:
A) This code does not compile:
int[] signed = new int[] { -100 };
uint[] unsigned = (uint[])signed;
B) Doing the cast in the debugger gives an error:
(uint[])signed
"Cannot convert type 'int[]' to 'uint[]'"
Sure enough, if line 3 was int[] instead of object then it would never compile. Which brings me to a final question related to Q2.
Q3) Why does C# raise a cast/conversion error in the debugger and compiler but not at runtime?