Object reference not set to an instance of an object. but the Properties are accessable

I am passing a IList into another class which looks as follows:

public class KundenViewModel
{
    public IList<Kunde> _kunden;

    /// <summary>
    /// Add a list of Kunde to the View
    /// </summary>
    /// <param name="kunden">A list of Kunde objects&开发者_高级运维lt;/param>
    public KundenViewModel(IList<Kunde> kunden)
    {
        foreach (var k in kunden)
        {
            var test = k._Name;
            _kunden.Add(k);
        }
        //_kunden.AddRange(kunden);
    }

    /// <summary>
    /// Add one Object of Kunde to the View
    /// </summary>
    /// <param name="kunde">A Kunde Object</param>
    public KundenViewModel(Kunde kunde)
    {
        _kunden.Add(kunde);
    }
}

But at runtime I receive at the Line 14 (_kunden.Add(k);) the error "Object reference not set to an instance of an object." Well I would say the object has never been initialized, but It has been and I also can access the properties for example the line before, there is no error.

Thanks in Advance

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Have you initialized _kunden list?

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Looks like _kunden is null. Where is it initialized?

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You have yet to initialise _kunden. You only declared it atm, meaning that you are currently trying to add k to null.

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The error message probably refers to the _kunden collection. It is probably not initialized.