ValidateCount is used to test the size of an array supplied to a parameter. The attribute expects a minimum and maximum length for the array.

ValidateCount only has meaning when applied to an array-type parameter, for example:

function Test-ValidateCount {
    [CmdletBinding()]
    param (
        [ValidateCount(1, 1)]
        [String[]]$Parameter1
    )
}

ValidateCount may also be applied to parameters that accept more advanced array types, such as [System.Collections.ArrayList] or [System.Collections.Generic.List[String]].