Question

I have Model like this

interface IStudent {
   string Name;
   List<Subjects> Marks;
   int RollNumber;
}

class ViewModel {
   ObservableCollection<IStudent> FromExcel;  
   ObservableCollection<IStudent> FromDB;
}

I need to bind the union of both collection on UI. Whats the best way. I was thinking of having another property ObservableCollection<IStudent> FromBoth; generated using LINQ Union method with comparer. My question is

1. Is it fine to have three collection to bind on UI? Note: I need to remove duplicates, giving priority to data from excel.

2. I need to pick some data from DB rather than excel in certain case.

For example: name=”hungrymind” in fromExcel and name=”hungrymind concepts” on fromDB collection. By default, grid on UI should show hungrymind (priority to excel), but if user uncheck column(aka property) from UI, then priority to data for that column becomes DB, i.e, UI should show “hungrymind concepts”

What should be approach to achieve this. My approach would be on user event, pick data from FromDB or FromExcel for each items in the collection and assign it to property in FromBoth collection. Since there are more than 100 columns, I had to use reflection, but wouldn’t be slow down the performance? If I avoid reflection, then I have to write a method for each column. Any suggestion on pattern or approach ?

Answer 1

I solved the issue like this

interface IStudent {
   string Name { get; set; }
   List<Subjects> Marks  { get; set; }
   int RollNumber  { get; set; }
}

class EntityViewModel: IStudent {
   IStudent FromExcel;  
   IStudent FromDB;
   public string Name {
     get { return Choose("Name").Name; }
     set { Choose("Name").Name = value; }
   }
   public string RollNumber{
     get { return Choose("RollNumber").RollNumber; }
     set { Choose("RollNumber").RollNumber = value; }
   }
   internal IStudent Choose(string propertyName){
     if(IsOveridable(propertyName))
        return this.FromExcel;
     else 
        return this.FromDB  
   }
}
class ViewModel{
   ObservableCollection<EntityViewModel> Entities;
}