StrategyAndFactory.cs

public interface IReport
{
    string Generate();
}

public class ReportA : IReport
{
    public string Generate()
    {
        return "Report A";
    }
}

public class ReportB : IReport
{
    public string Generate()
    {
        return "Report A";
    }
}

public enum ExampleEnum
{
    StrategyA,
    StrategyB,
}

public interface IReportFactory
{
    IReport GetInstance(ExampleEnum exampleEnum);
}

public class ReportFactory : IReportFactory
{
    public IReport GetInstance(ExampleEnum exampleEnum)
    {
        switch(exampleEnum)
        {
          case ExampleEnum.StrategyA:
            return new ReportA();
          case ExampleEnum.StrategyB:
            return new ReportB();
          default:
            // is there a default case? if yes, return it.
            // else throw an exception
            throw new NotImplementedException("");
        }
    }
}