Question

I am trying to create a disposable ADOX Catalog instance by implementing IDisposable interface but I am getting a Error which is:
ADOX.Catalog’ does not contain a definition for ‘Dispose’ and no extension method ‘Dispose’ accepting a first argument of type ‘ADOX.Catalog’ could be found (are you missing a using directive or an assembly reference?)

and this my code

namespace Disposable
{
class DBGen : IDisposable
{
    Catalog cat; 
    public DBGen()
    {
        cat = new Catalog();
        cat.Create("Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=D:\\AccessDB\\NewMDB.mdb;" +"Jet OLEDB:Engine Type=5");
        Console.WriteLine("Database Created Successfully");
        cat = null;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool b)
    {
        if (b)
        {
            cat.Dispose();
        }
    }
}

}

I am getting the error at

   cat.Dispose();

can you please let me know why this is happening? Thansk

Answer 1

The field cat seems to be set null right in the constructor so it’s null all the time.
Try to dispose ‘cut’ before you set it to null.

If you are going to use cat somwhere else in your class you should remove cat=null; from constructor and rewrite dispose like this:

public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool b)
    {
        if (b)
        {
            if (cat!=null) {
                var disposableCat = cat as IDisposable;
                if (disposableCat != null) {
                   disposableCat.Dispose();
                   cat=null;
                }
            }
        }
    }