Exception Filters (when)

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Exception Filters (when)

Exception Filters (when)

A when clause adds a boolean condition to a catch block, so it only handles the exception if that condition is also true. If the condition is false, C# looks at the next catch block as if this one didn't match at all. This avoids catching an exception just to immediately re-throw it based on some check.

Note: Exception filters are useful for handling the same exception type differently based on an error code or property.

Example: Exception Filters (when)

markup

using System;

class Program
{
    static void Main(string[] args)
    {
        try
        {
            throw new InvalidOperationException("critical failure");
        }
        catch (InvalidOperationException ex) when (ex.Message.Contains("critical"))
        {
            Console.WriteLine("Handled critical error: " + ex.Message);
        }
        catch (InvalidOperationException ex)
        {
            Console.WriteLine("Handled general error: " + ex.Message);
        }
    }
}

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Exception Filters (when)

Exception Filters (when)

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