By default, Import-CSV imports all values as strings, so to get DateTime- and integer-objects, we need to cast or parse them.

Using Foreach-Object:

> $listOfRows = Import-Csv .\\example.csv
> $listOfRows | ForEach-Object {
    #Cast properties
    $_.DateTime = [datetime]$_.DateTime
    $_.Integer = [int]$_.Integer

    #Output object
    $_
}

Using calculated properties:

> $listOfRows = Import-Csv .\\example.csv
> $listOfRows | Select-Object String,
    @{name="DateTime";expression={ [datetime]$_.DateTime }},
    @{name="Integer";expression={ [int]$_.Integer }}

Output:

String DateTime            Integer
------ --------            -------
First  01.12.2016 12:00:00      30
Second 03.11.2015 13:00:00      20
Third  05.12.2015 14:00:00      20