Question

I am currently creating a C# application that supports MySQL and MSSQL databases. The problem I am having is with my wrapper. I have my code working for MySQL, but I am having issues modifying it to support multiple databases.

If you take a look at a stripped down version of my code you will see I have a dbConn object of type DBMySQL, which is fine if I only want MySQL Support. I need modify DBMySQL to be something generic so that I can run dbConn = new DBMySQL(…) and dbConn = DBMSSQL(…) and then I can simply call dbConn.SomeMethod() and have it work on the appropriate database. I would prefer to keep this same setup as much as possible as I have other things in my DBMySQL and DBMSSQL classes for bulk inserting into databases and specific error checking.

I was thinking / trying to declare something like Object dbConn, then manipulating that, but that did not go so well. Then I tried to use an enum class of object types, but I had issues with that as well. I know there are many third party libraries that do all of this but I would prefer to use my own code.

Does anyone have any suggestions how I might modify my DBWrapper to solve this problem?

//WRAPPER CLASS THAT CALLS DBMySQL, ISSUE IS I NOW NEED TO SUPPORT 
//DBMSSQL as well, not just DBMySQL
class DBWrapper
{
    DBMySQL dbConn;

    public DBWrapper(...,string type)
    {
        if(type.Equals("MySQL")
        {
            dbConn = new DBMySQL(...);
        }
        //NEED TO REWORK TO SUPPORT THIS BELOW!!
        else if(type.Equals("MSSQL")
        {
            //NEED TO MODIFY TO SUPPORT MSSQL
            //ISSUE IS DbConn is of type DBMySQL
            //SO I CANNOT GO
            // DbConn = new DBMSSQL(...);
            // any ideas?
        }   
    }

    public void setQuery(string myquery)
    {
            dbConn.setQuery(myquery);
    }
}

class DBMySQL
{
    public string dbinfo;
    string query;

    public DBMySQL(...)
    {
        dbinfo = ...;

    }

    public void setQuery(...)
    {
        query = myquery;
    }
}

//NEED TO RE-WORK WRAPPER TO SUPPORT THIS
class DBMSSQL
{
    public string dbinfo;
    string query;

    public DBMSSQL(...)
    {
        dbinfo = ...;

    }

    public void setQuery(...)
    {
        query = myquery;
    }
}

At this point I would appreciate any help at all, so if you are viewing this post and have an idea, please let me know as I have already spent all day on this.

Answer 1

What you need is to create interface which would describe what you want your data access classes to do.

E.g. from your sample

public interface IDBAccess
{
     void setQuery(...);
}

public class DBMySQL : IDBAccess
{
    public string dbinfo;
    string query;

    public DBMySQL(...)
    {
        dbinfo = ...;

    }

    public void setQuery(...)
    {
        query = myquery;
    }
}

public class DBMSSQL : IDBAccess
{
    public string dbinfo;
    string query;

    public DBMSSQL(...)
    {
        dbinfo = ...;

    }

    public void setQuery(...)
    {
        query = myquery;
    }
}

At this point you will be able to do this:

IDBAccess dbConn;
dbConn = new DBMySQL();
dbConn = new DBMSSQL();

Having in mind that you are new to this it may not be useful to suggest that you take a look at NHibernate or Castle ActiveRecord and Castle Windsor. But have them in mind for future.