Question

At first sorry for my really bad title! If you have a better title just change it or make a comment =)

I have this class:

public class Config
{
    public Provider1 Provider1 { get; set; }
    public Provider2 Provider2 { get; set; }
    public Provider3 Provider3 { get; set; }
    public Provider4 Provider4  { get; set; }
    public Provider5 Provider5 { get; set; }

    public int GetNumber(string provider)
    {
        ...
    }
}

Each provider has a Number property:

public interface IProvider
{
    int Number{ get; set; }
}

In dependency of the provider I want to return the Number of the provider.

How would you do that?

I do not want to use a big switch block.

Answer 1

public interface IProvider
{
  int Number {get;set;}
}

public class Config
{
     public int GetNumber<T>() where T : IProvider
     {
         // code to find the provider you want
         IProvider foundProvider = ProviderFactoryMethodHere(typeof(T));

         return foundProvider.Number;
     }
}

Now all of your provider classes need to implement the IProvider interface and you need to implement a factory that will return the correct provider to you given the type that you’ve requested in the generic method.

// Test code example
Config configImpl = new Config();
int numberOfProvider = configImpl.GetNumber<Provider1>();
Assert.Equal(1, numberOfProvider);

I’ll add a simple ProviderFactoryMethod example. Note that we could also make this method generic instead of passing the type as a parameter, but I’ll leave the example as is.

public IProvider ProviderFactoryMethodHere(Type providerRequested)
{
    Dictionary <Type, IProvider> providerDict;
    if (providerDict == null)
    {
      // populate dictionary with providers, keyed by their type
      providerDict = new Dictionary<Type, IProvider>();
      providerDict.Add(typeof(Provider1), new Provider1());

      // repeat for all providers, this is pretty simple but definitely works
      // we could use other ways of holding on to your provider instances
    }
    if (providerDict.HasKey(providerRequested))
    {
        return providerDict[providerRequested];
    }
    // could throw exception here if you want to use that kind of error
    // handling, but we'll just return null for now
    return null;
}

Cheers.