C# initialize a class with array of another complex type

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C#

Team, in C# don't know how to initialize below SiteExternalId Class with some dummy values, help me

public class SiteExternalId
{
    public SiteExternalIdItem[] Item { get; set; }
}

public class SiteExternalIdItem
{
    public ExternalTypeCd ExternalIdTypeCd { get; set; }

    public string SiteNumber { get; set; }
}

public class ExternalTypeCd
{
    public string ExternalIdTypeName { get; set; }

    public string SiteCode { get; set; }
}

What I have tried:

I'm trying this way, but not success

SiteExternalId = new SiteExternalId
{
    Item = new SiteExternalIdItem[]
    {
        new ExternalTypeCd {ExternalIdTypeName = "A", SiteCode = "X"}
    }
}

If possible could you give me initialization in a single line. Thanks