Complete set: Intro to C - Bill Buchanan

2.4 Casting Objects
Sometimes we need to cast objects.
We may cast up or down the object hierarchy.
Casting down is dangerous and may result in a run time error.
Examples of casting Objects
Object sr0 = new StreamReader("file.txt");
Object ht0 = new Hashtable();
// Following fails at compile time
// StreamReader f1 = sr0;
StreamReader f2 = (StreamReader)sr0;
// Following generates run time error
StreamReader f3 = (StreamReader)ht0;
2.4.1 Self-test
For each of the following decide if the line will work OK or fail at design time or fail
at run time.
Which of these will compile and run
int i0 = 3.1;
string s0 = 'x';
char c0 = 'c';
string s1 = "x" + 'y';
char c1 = (char) "a";
float f0 = 3;
Compile Error
duction to .NET
Intro
float f1 = "3.1";
DateTime v0 = DateTime.Now;
Object v1 = DateTime.Now;
Object v2 = new Object();
DateTime v3 = (DateTime) new Object();
DateTime v4 = new Object();
OK
OK
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