Using Exception Filters in C#: Implementing Conditional Exception Handling

Enhance your C# error handling with exception filters. This tutorial explains how to use the `when` keyword to add conditions to `catch` blocks, enabling more precise and efficient exception handling based on specific exception types or properties, leading to more robust applications.

Using Exception Filters in C#

C# exception filters (introduced in C# 6.0) allow you to add conditions to your `catch` blocks. A `catch` block will only execute if the associated condition (filter) evaluates to `true`. This provides a more refined way to handle exceptions.

Exception Filters and the `when` Keyword

Exception filters use the `when` keyword to specify a condition. The syntax is:

catch (ExceptionType e) when (condition) {
    // Code to execute if the exception is of type ExceptionType and the condition is true
}

If the condition is `false`, the `catch` block is skipped, and the next `catch` handler (if any) is checked.

Example 1: Filtering by Exception Type

This example demonstrates filtering based on the exception type:

try {
    // Code that might throw an IndexOutOfRangeException
} catch (Exception ex) when (ex is IndexOutOfRangeException) {
    Console.WriteLine("Index out of range!");
}

Example 2: Filtering by Exception Message

This example filters based on the exception's message:

try {
    throw new Exception("Specific error message");
} catch (Exception ex) when (ex.Message == "Specific error message") {
    Console.WriteLine("The specific error occurred!");
}

Using Exception Filters for Logging

Exception filters are often used for logging purposes. You can use them to log specific types of exceptions or exceptions with specific messages without adding complex conditional logic within the catch block itself.