C# try Statements and Exceptions
Description
A try statement specifies a code block subject to error-handling or cleanup code.
The try block must be followed by a catch block, a finally block, or both.
The catch block executes when an error occurs in the try block.
The finally block performs cleanup code, whether or not an error occurred.
Syntax
A try statement looks like this:
try/*w w w . ja v a 2 s .c om*/
{
... // exception may get thrown within execution of this block
}
catch (ExceptionA ex)
{
... // handle exception of type ExceptionA
}
catch (ExceptionB ex)
{
... // handle exception of type ExceptionB
}
finally
{
... // cleanup code
}
Example
Consider the following program. Because x is zero, the runtime throws a DivideByZeroException, and our program terminates. We can prevent this by catching the exception as follows:
using System;//from w w w. j a v a 2 s. co m
class Test
{
static int Calc (int x) { return 10 / x; }
static void Main()
{
try
{
int y = Calc (0);
Console.WriteLine (y);
}
catch (DivideByZeroException ex)
{
Console.WriteLine ("x cannot be zero");
}
Console.WriteLine ("program completed");
}
}
The code above generates the following result.
Example 2
using System; //from w w w .j a v a 2 s. c o m
class MainClass {
public static void Main() {
int[] numer = { 4, 8, 16, 32, 64, 128, 256, 512 };
int d = 0;
try { // outer try
for(int i=0; i < 10; i++) {
try { // nested try
Console.WriteLine(numer[i] + " / " +
numer[i] + " is " +
numer[i]/d);
}
catch (DivideByZeroException) {
// catch the exception
Console.WriteLine("Can't divide by Zero!");
}
}
}
catch (IndexOutOfRangeException) {
// catch the exception
Console.WriteLine("No matching element found.");
Console.WriteLine("Fatal error -- program terminated.");
}
}
}
The code above generates the following result.
