Understanding Generic Class implementation

Question

I am trying to understand this code: public interface IBuilding { string Id { get; } } public class Model where TBuilding : IBuilding { public TBuilding Building { get; private set; } } What does Model mean here? From my understanding, ClassName stands for Generic Class. can represent string, int etc. But implements IBuilding interface here. Why does a generic type implement an interface? My suspicion is that means . Am I correct? I have no clue on how to understand this code. I read up on Generic Classes but could not find anything useful.

T.S. · Answer

This is a little misleading by naming

public interface IBuilding // interface contract
{
    string Id { get; }
    string ElevatorCount { get; }
}

// this is where you have confusion. T - is standard naming for generic type parameter
// if you start naming your generic type parameter TBuilding - 
// you will get confused that it might be some type
public class BuildingInspector<T>  where T : IBuilding // T : IBuilding - restricts types to IBuilding
{
    public BuildingInspector(T building) // generic type in constructor
    {
        Building = building;
    }

    public T Building { get; private set; }
    public int GetTotalElevatorCapacity(int kiloPerElevator)
    {
        return (this.Building.ElevatorCount * kiloPerElevator)  
    }
}

// U S A G E

public class SingleFamilyHome : IBuilding
{
    public string Id { get; private set; }
    public string ElevatorCount { get; private set; }
}
 . . . . .
private void TryUsingGenericType ()
{

    var famHome = new SingleFamilyHome(){ Id=1, ElevatorCount=0 };
    var famInspector = new BuildingInspector<SingleFamilyHome>(); // SUCCESS

    var capacity = famInspector.GetTotalElevatorCapacity(0);

    // this code will not compile because above you have --> where T : IBuilding
    var stringInspector = new BuildingInspector<string>(); // DESIGN TIME ERROR

}

Now that you see declaration AND usage, you can see how it is used. Best example is System.Collections.Generic.List<T>. You can have any list

List<string>
List<Building>
List<int>

Bujor Iosif · Answer

'Where' syntax is constraining your T type to be a type that implements IBuilding. Without the where condition, it would accept any types. Here you can find a more detailed explanation.
https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/where-generic-type-constraint

Daniel A. White · Answer

Not exactly. T is just a placeholder for a type. If you have FireHouse, PoliceStation, Hospital, etc. implementing IBuilding you can provide one of those to Model and the Building property would only hold an instance of that type.

Understanding Generic Class implementation

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