Cast IList to List

Try

List<SubProduct> subProducts = new List<SubProduct>(Model.subproduct);

or

List<SubProduct> subProducts = Model.subproducts as List<SubProduct>;

How about this:

List<SubProduct> subProducts = Model.subproduct.ToList();

List<SubProduct> subProducts= (List<SubProduct>)Model.subproduct;

The implicit conversion failes because List<> implements IList, not viceversa. So you can say IList<T> foo = new List<T>(), but not List<T> foo = (some IList-returning method or property).

If you have an IList containing interfaces, you can cast it like this:

List to IList

List<Foo> Foos = new List<Foo>(); 
IList<IFoo> IFoos = Foos.ToList<IFoo>();

IList to List

IList<IFoo> IFoos = new List<IFoo>();
List<Foo> Foos = new List<Foo>(IFoos.Select(x => (Foo)x));

This assumes Foo has IFoo interfaced.

The other answers all recommend to use AddRange with an IList.

A more elegant solution that avoids the casting is to implement an extension to IList to do the job.

In VB.NET:

<Extension()>
Public Sub AddRange(Of T)(ByRef Exttype As IList(Of T), ElementsToAdd As IEnumerable(Of T))
   For Each ele In ElementsToAdd
      Exttype.Add(ele)
   Next
End Sub

And in C#:

public void AddRange<T>(this ref IList<T> Exttype, IEnumerable<T> ElementsToAdd)
{
    foreach (var ele in ElementsToAdd)
    {
        Exttype.Add(ele);
    }
}

    public async Task<List<TimeAndAttendanceShift>> FindEntitiesByExpression(Expression<Func<TimeAndAttendanceShift, bool>> predicate)
    {
        IList<TimeAndAttendanceShift> result = await _dbContext.Set<TimeAndAttendanceShift>().Where(predicate).ToListAsync<TimeAndAttendanceShift>();

        return result.ToList<TimeAndAttendanceShift>();
    }

This is the best option to cast/convert list of generic object to list of string.

object valueList;
List<string> list = ((IList)valueList).Cast<object>().Select(o => o.ToString()).ToList();