ValidateDrive may be used to test the drive letter provided for a parameter that accepts a path. ValidateDrive handles both relative and absolute paths. A relative path is resolved to a full path before it is tested against the supplied drive letters. When using the ValidateDrive attribute, the parameter type must be String. The parameter cannot be omitted:

function Test-ValidateDrive {
    [CmdletBinding()]
    param (
        [ValidateDrive('C')]
        [String]$Parameter1
    )
}

ValidateDrive cannot act on an array of paths; if the parameter type is an array, an error will be thrown stating the path argument is invalid.