Question

I have following interface That I am implementing

    interface IReport <TOutput>
    {
        List<TOutput> GenerateReport<TInput>(TInput input);
    }

In my implementation of this function

I want the output be FeederPerformanceErrorEntry type and input type be Tuple<int, int, bool>

What I am doing wrong ?

public List<FeederPerformanceErrorEntry> GenerateReport< FeederPerformanceErrorEntry , Tuple<int, int, bool> >(Tuple<int, int, bool> tuple)

Thanks

Answer 1

That’s not how generic methods work. If you have a generic interface, you can say that your class that implements that interface is not generic and has some specific type parameters.

But you can’t do the same for generic methods. Those always have to work for any type (or any type that satisfies specified constraints, if you have them). Although “work” here may mean “throw an exception”.

So, you could implement that method like this:

public List<FeederPerformanceErrorEntry> GenerateReport<TInput>(TInput input)
{
    if ((typeof(TInput) != typeof(Tuple<int, int, bool>))
        throw new InvalidOperationException();

    // rest of your code here
}

But if you want to do that, you don’t actually need generic method. It would be better if you changed the interface (if you can) to:

interface IReport<TInput, TOutput>
{
    List<TOutput> GenerateReport(TInput input);
}

And then implement the class as:

class FeederReport : IReport<Tuple<int, int, bool>, FeederPerformanceErrorEntry>
{
    public List<FeederPerformanceErrorEntry> GenerateReport(Tuple<int, int, bool> input)
    {
        // your code here
    }
}

If you are able to create the report from several different input types, you can always implement the interface several times:

class FeederReport : IReport<Tuple<int, int, bool>, FeederPerformanceErrorEntry>,
                     IReport<Feeder, FeederPerformanceErrorEntry>