public int Alternate1RowBackgroundCount {get; set;}

//Modify an existing tableframe using CIM properties.

//Reference the active layout
Layout layout = LayoutView.Active.Layout;

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  //Reference table frame
  TableFrame TF = layout.FindElement("Table Frame") as TableFrame;

  //Modify CIM properties
  CIMTableFrame cimTF = TF.GetDefinition() as CIMTableFrame;
  cimTF.Alternate1RowBackgroundCount = 1;
  cimTF.Alternate2RowBackgroundCount = 1;

  //Apply the changes
  TF.SetDefinition(cimTF);
});