Change ModelState Value in MVC and .Net Core

Sample Model

public class State
    {
        public int State_Id { get; set; }
        public string State_Title { get; set; }
    }
    public class City
    {
        public int City_Id { get; set; }
        public string City_Title { get; set; }
        public State state { get; set }
    }

ASP.NET - MVC

ModelState.SetModelValue("City_Id", new ValueProviderResult("Change City ID", "", CultureInfo.InvariantCulture));
ModelState.SetModelValue("City_Title", new ValueProviderResult("Change Title", "", CultureInfo.InvariantCulture));
ModelState.SetModelValue("state.State_Id", new ValueProviderResult("Change State Id", "", CultureInfo.InvariantCulture));
ModelState.SetModelValue("state.State_Title", new ValueProviderResult("Change Title", "", CultureInfo.InvariantCulture));

ASP.NET - CORE MVC

ModelState.SetModelValue("City_Id", new ValueProviderResult("New Value", CultureInfo.InvariantCulture));
ModelState.SetModelValue("City_Title", new ValueProviderResult("New Value", CultureInfo.InvariantCulture));
ModelState.SetModelValue("state.State_Id", new ValueProviderResult("New Value", CultureInfo.InvariantCulture));
ModelState.SetModelValue("state.State_Title", new ValueProviderResult("New Value", CultureInfo.InvariantCulture));

Clear Or Reset ModelState

ModelState.Clear();