# Custom Exception

An application-specific exception type created by extending an exception class.

## What is **Custom Exception** in C#?

**Custom Exception** — An application-specific exception type created by extending an exception class.

```csharp
class Reservation
{
    void Reserve(int seats)
    {
        if (seats < 1)
        {
            throw new ArgumentException("Seat count must be positive");
        }
    }
}
```

Level: Journeyman · [More C# terms at this level](https://www.ask-codey.com/glossary/subjects/c-sharp/journeyman)

Updated: September 27, 2026

## In other subjects

- [Custom Exception in Java](https://www.ask-codey.com/glossary/custom-exception-java)

Source: https://www.ask-codey.com/glossary/custom-exception-c-sharp