Generic method to read values from any type of Form fields

         private static Dictionary<Guid, string> FormFieldsToDictionary(IList<IViewModel> fields)
		{
			Dictionary<Guid, string> fielDictionary = new Dictionary<Guid, string>();
			foreach (var field in fields)
			{
				fielDictionary.Add(Guid.Parse(field.ItemId), field.GetType().GetProperty("Value")?.GetValue(field, null)?.ToString() ?? string.Empty);
			}
			return fielDictionary;
		}

	private static string GetValue(IViewModel field)
		{
			if (field == null)
			{ return default(string); }


			if ((field as StringInputViewModel) != null)
			{
				return (string)(object)(field as StringInputViewModel).Value;
			}

			if (field is ListViewModel)
			{
				var listField = (ListViewModel)field;
				var array = listField?.Value?.ToArray();
				if (array == null)
				{
					return string.Empty;
				}
				return String.Join(",", array);
			}

			if (field is DateViewModel)
			{
				var dateField = (DateViewModel)field;
				return dateField.Value.HasValue ? dateField.Value.Value.ToShortDateString() : string.Empty;
			}

			if (field is NumberViewModel)
			{
				var numberField = (NumberViewModel)field;
				return numberField.Value.HasValue ? numberField.Value.ToString() : string.Empty;
			}

			if (field is TextViewModel)
			{
				var textField = (TextViewModel)field;
				return (string)(object)textField.Text;
			}

			if (field is CheckBoxViewModel)
			{
				var checkbox = (CheckBoxListViewModel)field;
				return (string)(object)checkbox.Value;
			}


			return default(string);
		}

protected override bool Execute(UpdateContactData data, FormSubmitContext formSubmitContext)
		{
			var fieldsDictionary = FormFieldsToDictionary(formSubmitContext.Fields);

           // From here you can create a model from fieldsDictionary, call any API and return call status

       }