Question

Hi I am wanting to create a base class to inherit from but I am having some problems.

I have two classes which do almost identical work but get the data which they work with from different databases and use different internal data structures to manipulate the data.
I want to have virtual doSomething method in the base and ideally virtual dataAccess method in the base also.

The second problem can be solved through the use of generics but I cant use generics to solve the first problem as the constructor of the DBMl context I use is not parameterless.

Am I going about this all wrong. I am trying to be DRY but seem to be working against inheritance.

Example code below.

class Foo    {
private _ctx DBML.Database1; // Inherits from System.Data.Linq.DataContext

public Foo(string constring)    {
    _ctx = new DBML.Database1(constring);
}

private DoSomeThing()   {

    FooDataObj = DataAccess(1);
}

private FooDataObj DataAccess(int ID)
{
    var v = from t in _ctx
            where t.Id = ID
            select new FooDataObj(t);

    return v
}
}

class Bar    {
private _ctx DBML.Database2; // Inherits from System.Data.Linq.DataContext

public Bar(string constring)
{
    _ctx = new DBML.Database2(constring);
}

private DoSomeThing()   {

    BarDataObj = DataAccess(1);
}

private BarDataObj DataAccess(int ID)   {
    var v = from t in _ctx
            where t.Id = ID
            select new BarDataObj(t);

    return v
}
}

Answer 1

Foo and Bar should not call the database constructor by themselves, the database object should be a parameter of the constructor (instead of the connection string). This principle is called Dependency Injection and will solve most of your problems. Should be easy then to create a new generic class DataObjFactory<DataObjType> as a replacement for Foo and Bar.