Setting private key on x509 certificate always throws PlatformNotSupportedException

Looking at this code in X509Certificate2.cs:

`public AsymmetricAlgorithm PrivateKey
{
get
{
this.ThrowIfInvalid();
if (!this.HasPrivateKey)
return (AsymmetricAlgorithm) null;
if (this._lazyPrivateKey == null)
{
switch (this.GetKeyAlgorithm())
{
case "1.2.840.113549.1.1.1":
this._lazyPrivateKey = (AsymmetricAlgorithm) this.Pal.GetRSAPrivateKey();
break;
case "1.2.840.10040.4.1":
this._lazyPrivateKey = (AsymmetricAlgorithm) this.Pal.GetDSAPrivateKey();
break;
default:
throw new NotSupportedException(SR.NotSupported_KeyAlgorithm);
}
}
return this._lazyPrivateKey;
}
set
{
throw new PlatformNotSupportedException();
}
}`

It would appear that trying to set the private key of a cert will always throw an exception, regardless of platform, despite the documentation and tooltip stating that the private key can be set via this property.