Append a Lists Contents to another List C#

I have the following:

1. A main List called GlobalStrings
2. Another List called localStrings

In a loop for example:

List<string> GlobalStrings = new List<string>(); 
List<string> localStrings = new List<string>();
for(x=1;x<10;x++)
{
    localStrings.Add("some value"); 
    localStrings.Add("some value");
}
// Want to append localStrings to GlobalStrings as easily as possible

Solution 1:

GlobalStrings.AddRange(localStrings);

Note: You cannot declare the list object using the interface (IList).
Documentation: List<T>.AddRange(IEnumerable<T>).

Solution 2:

GlobalStrings.AddRange(localStrings);

That works.

Documentation: List<T>.AddRange(IEnumerable<T>).

Solution 3:

Try AddRange-method:

GlobalStrings.AddRange(localStrings);

Solution 4:

With Linq

var newList = GlobalStrings.Append(localStrings)

Solution 5:

Here is my example:

    private List<int> m_machinePorts = new List<int>();

    public List<int> machinePorts
    {
        get { return m_machinePorts; }
    }

    Init()
    {
        // Custom function to get available ethernet ports
        List<int> localEnetPorts = _Globals.GetAvailableEthernetPorts();

        // Custome function to get available serial ports
        List<int> localPorts = _Globals.GetAvailableSerialPorts();

        // Build Available port list 
        m_machinePorts.AddRange(localEnetPorts);
        m_machinePorts.AddRange(localPorts);
     }