C# Exception Filters

by Online Tutorials Library July 22, 2022

C# Exception Filters

C# Exception Filters is a feature of C# programming language. It is introduced in version C# 6.0. It allows us to specify condition along with a catch block.

C# provides when keyword to apply a condition (or filter) along with catch block.

A catch block will execute only when the condition is true. If the condition is false, catch block is skipped and compiler search for next catch handler.

C# Exception Filters is used for logging purpose.

C# Exception Filter Syntax

In the following example, we are implementing exception filter. It executes only, if compiler throws an IndexOutOfRangeException exception.

C# Exception Filter Example

 using System; namespace CSharpFeatures {     class ExceptionFilter     {         public static void Main(string[] args)         {             try             {                 int[] a = new int[5];                 a[10] = 12;             }catch(Exception e) when(e.GetType().ToString() == “System.IndexOutOfRangeException”)             {                 // Executing some other task                 SomeOtherTask();             }         }         static void SomeOtherTask()         {             Console.WriteLine(“A new task is executing…”);         }     } } 

Output

A new task is executing...

In the following example, we are throwing exception explicitly that matches with when condition.

C# Exception Filter Example2

 using System; namespace CSharpFeatures {     class ExceptionFilter     {         public static void Main(string[] args)         {             try             {                 // Throwing Exception explicitly                 throw new IndexOutOfRangeException(“Array Exception Occured”);             }catch(Exception e) when(e.Message == “Array Exception Occured”)             {                 Console.WriteLine(e.Message);                 SomeOtherTask();             }         }         static void SomeOtherTask()         {             Console.WriteLine(“A new task is executing…”);         }     } } 

Output

Array Exception Occured A new task is executing...

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