Checking whether an enum value exists by an integer reference in C#

Say you have the following ShipmentOption enumeration:

public enum ShipmentOption
{
	Land,
	Sea,
	Air
}

By default each enumeration value will have an integer representation starting with 0. So 0 corresponds to Land, 1 to Sea and 2 to Air. Imagine that a method accepts the numeric value like this:

public void SendShipment(int numericShipmentType)

Then the incoming numeric parameter could be anything. How can we check whether an integer has a corresponding enumeration value?

The following code will do just that:

public void SendShipment(int numericShipmentType)
{
	if (Enum.IsDefined(typeof(ShipmentOption), numericShipmentType))
	{
		Console.WriteLine("This type is defined: {0}", (ShipmentOption)numericShipmentType);
	}
	else
	{
		throw new InvalidEnumArgumentException("ShipmentOption", numericShipmentType, typeof(ShipmentOption));
	}
}

The InvalidEnumArgumentException class is defined in the System.ComponentModel namespace.

Passing in 2 will result in the following output:

This type is defined: Air

An invalid integer argument will throw an exception:

The value of argument ‘ShipmentOption’ (5) is invalid for Enum type ‘ShipmentOption’.

View all various C# language feature related posts here.