Why Doesn't Casting an Invalid Integer to an Enum in C# Throw an Exception?

Why Casting Int to Invalid Enum Value DOES NOT Throw Exception

In C#, enums are essentially numeric types that map a set of named values to integer constants. An intriguing aspect of enums is their ability to accept any integer value, including values that fall outside their defined range.

When you encounter an enum like:

enum Beer
{
    Bud = 10,
    Stella = 20,
    Unknown
}

You might expect that casting an integer that's not 10, 20, or Unknown to the Beer type would throw an exception. However, this is not the case. Casting an invalid integer to a Beer type results in the assignment of that integer value to the enum variable.

Consider the following code:

int i = 50;
var b = (Beer) i;

Console.WriteLine(b.ToString());

When you run this code, it outputs "50" to the console. The b variable is assigned the integer value 50, which is not a valid enum value for Beer. However, the cast does not throw an exception.

This behavior stems from a design decision made by the creators of the .NET Framework. Enums are backed by other value types, such as int, short, or byte. As a result, they can accept any value that is valid for those underlying value types.

While this behavior can be convenient in some scenarios, it can also lead to unexpected results if you're not aware of it.

Beyond the Default Behavior

For situations where you require more strict enforcement of enum values, there are utilities and extensions you can use to validate and enforce the use of defined enum values only. These tools can help you avoid potential errors and ensure that your enum variables hold only the intended values.

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