C# try Keyword (Begins Protected Region of Code)

Use the try keyword. This keyword describes protected regions of code.
Try. The try keyword begins an exception handling block. Control flow enters a protected region. If an error occurs in a statement in a try block, another path may be reached.
We already know that try is used to implement exception handling, but it is useful to take a closer look. Try is implemented with a special instruction in the intermediate language.CatchException
An example. In this program, 2 methods are present. We see the A method, which uses the try and catch keywords, and the B method, which does not.

And: In the A method, the try keyword denotes that a protected region of code begins.

Note: This means when the DivideByZeroException is thrown, the catch block will be entered.

DivideByZeroException
C# program that shows try keyword using System; class Program { static void Main() { A(); B(); } static void A() { try { int value = 1 / int.Parse("0"); } catch { Console.WriteLine("A"); } } static void B() { int value = 1 / int.Parse("0"); Console.WriteLine("B"); } } Output A Unhandled Exception: System.DivideByZeroException: Attempted to divide by zero. at Program.B() in C:\...\Program.cs:line 25 at Program.Main() in C:\...\Program.cs:line 8
Protected regions. We next look at the intermediate representation (IL). When a method uses exception handling, the IL shows an ending descriptor (.try, to, catch object handler, to).IL

Note: This tells the virtual execution engine how to execute the statements in the method in those ranges.

Intermediate representation for A: IL .method private hidebysig static void A() cil managed { .maxstack 2 L_0000: ldc.i4.1 L_0001: ldstr "0" L_0006: call int32 [mscorlib]System.Int32::Parse(string) L_000b: div L_000c: pop L_000d: leave.s L_001c L_000f: pop L_0010: ldstr "A" L_0015: call void [mscorlib]System.Console::WriteLine(string) L_001a: leave.s L_001c L_001c: ret .try L_0000 to L_000f catch object handler L_000f to L_001c }
Notes, opcodes. There is no "try" opcode instruction in the same way there is a call instruction. Exception handling is built into the execution engine at all levels.

And: The engine knows at every statement whether it is inside a protected region.

Thus: Try is a keyword that modifies many statements, not an imperative opcode.

Finally. The try keyword is not only used to deal with potential errors. It is also used with finally. A finally block executes always after the completion of the try block statements.Finally

Here: In this program, no errors occur. It is unlikely that Console.WriteLine will throw an exception here.

And: The try-finally blocks are likely unnecessary. The program shows the try statement's use in the absence of exceptions.

Console.WriteLine
C# program that uses try with finally using System; class Program { static void Main() { try { Console.WriteLine("A"); } finally { Console.WriteLine("B"); } } } Output A B
A summary. We used the try keyword. And we tried to understand its implementation. It specifies a range of protected statements, and is always used with catch or finally.
This functionality is built into the virtual execution engine at a deep level. Try is an important and useful C# keyword. It helps with the development of error-proof, reliable code.
© 2007-2019 Sam Allen. Every person is special and unique. Send bug reports to info@dotnetperls.com.
HomeSearch
Home
Dot Net Perls