Your code should look like this.
private var packages = new List<Package>();
public List<Package> Packages
{
set { packages = value; }
get { return packages; }
}
If you're trying to use the index getter/setter for some kind of passthrough:
public int this[int key]
{
get
{
return Packages[key];
}
set
{
Packages[key] = value;
}
}