How can I design this better? (Avoiding a switch statement with Object Oriented design)

Question

I know a little bit about Object Oriented design, but I\'m not sure how to go about using those principles in my code. Here\'s what I\'m working on:

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Answer 1

Is Agency a class you control? If so do something like this:

public abstract class GenericDb
{
    public abstract void Query(parms);
}

In your Agency Class, you could have

public GenericDb ClientDb {get; set;}

Then have a SqlDb class like:

public class SqlDb : GenericDb
{
    public void Query(parms);
}

public class PicDb : GenericDb
{
    public void Query(parms);
}

Then this code:

public void Query(Agency agency, Citation queryCitation) {
        queryCitation.AgencyCode = agency.AgencyCode;

        switch (agency.ClientDb.Type) {
            case "SQL":
                QueryOracle(agency, queryCitation);
                break;
            case "PIC":
                QueryPick(agency, queryCitation);
                break;
        }
    }

becomes

public void Query(Agency agency, Citation queryCitation) {
        queryCitation.AgencyCode = agency.AgencyCode;
        agency.ClientDb.Query(queryCitation);
    }

Because of inheritance, it will know that ClientDb has a base class of GenericDb. It will know by the type of the ClientDb parameter whether it should run the SqlDb or the PicDb or Oracle etc.