Using the exception object C# with Example

You are allowed to create and throw exceptions in your own code. Instantiating an exception is done the same way 
that any other C# object. 
 

Exception ex = new Exception(); 
// constructor with an overload that takes a message string 
Exception ex = new Exception("Error message"); 
You can then use the throw keyword to raise the exception: 
try 
{ 
throw new Exception("Error"); 
} 
catch (Exception ex) 
{ 
Console.Write(ex.Message); // Logs 'Error' to the output window 
} 
Note: If you're throwing a new exception inside a catch block, ensure that the original exception is passed as "inner 
exception", e.g. 
void DoSomething() 
{ 
int b=1; int c=5; 
try 
{ 
var a = 1; 
b = a - 1; 
c = a / b; 
a = a / c; 
} 
catch (DivideByZeroException dEx) when (b==0) 
{ 
// we're throwing the same kind of exception 
throw new DivideByZeroException("Cannot divide by b because it is zero", dEx); 
} 
catch (DivideByZeroException dEx) when (c==0) 
{ 
// we're throwing the same kind of exception 
throw new DivideByZeroException("Cannot divide by c because it is zero", dEx); 
} 
} 
void Main() 
{ 
try 
{ 
DoSomething(); 
} 
catch (Exception ex) 
{ 
// Logs full error information (incl. inner exception) 
Console.Write(ex.ToString()); 
} 
} 
In this case it is assumed that the exception cannot be handled but some useful information is added to the 
message (and the original exception can still be accessed via ex.InnerException by an outer exception block). 
It will show something like: 
 

System.DivideByZeroException: Cannot divide by b because it is zero ---> System.DivideByZeroException: 
Attempted to divide by zero. 
at UserQuery.g     DoSomething0_0() in C:[...]\LINQPadQuery.cs:line 36 
--- End of inner exception stack trace --- 
at UserQuery.g DoSomething0_0() in C:[...]\LINQPadQuery.cs:line 42 
at UserQuery.Main() in C:[...]\LINQPadQuery.cs:line 55 
If you're trying this example in LinqPad, you'll notice that the line numbers aren't very meaningful (they don't 
always help you). But passing a helpful error text as suggested above oftentimes significantly reduces the time to 
track down the location of the error, which is in this example clearly the line 
c = a / b; 
in function DoSomething(). 
Try it in .NET Fiddle