Re: confusion on interface IDataReader

Ahhh, duh!  Thanks for clearing that up Joe.  I was seeing the same thing
for IDbCommand and it puzzled me.  Now it makes sense.

Peter

> -----Original Message-----
> From: Discussion relating to the specifics of the C# and
> Managed C++ languages [mailto:[email protected]]
> On Behalf Of Joe Mayo
> Sent: Tuesday, June 06, 2006 4:42 PM
> To: [email protected]
> Subject: Re: [DOTNET-CX] confusion on interface IDataReader
>
> Hi Peter,
>
> SqlCommand.ExecuteReader will return a SqlDataReader.  Since
> SqlDataReader implements the IDataReader interface, it can be
> assigned to a variable of the IDataReader interface type, but
> it is still a SqlDataReader.
>
> Joe
> http://www.csharp-station.com
>
> > -----Original Message-----
> > From: Discussion relating to the specifics of the C# and
> Managed C++
> > languages [mailto:[email protected]] On Behalf Of Peter
> > Osucha
> > Sent: Tuesday, June 06, 2006 2:33 PM
> > To: [email protected]
> > Subject: [DOTNET-CX] confusion on interface IDataReader
> >
> > I was looking over some example code that was handling data
> access to
> > a SQL db.  A method for the code was similar to....
> >
> > public IDataReader PerformStoredProcedure_DataReader (
> string spName,
> > CommandBehavior behavior ) {
> >     IDataReader result = null;
> >     SqlCommand cmd = new SqlCommand ( spName,
> (SqlConnection)Connection );
> >     cmd.CommandType = CommandType.StoredProcedure;
> >     result = cmd.ExecuteReader ( behavior );
> >     return result;
> > }
> >
> > Now what has me confused is that this method returns an
> object of type
> > IDataReader - which I thought (from reviewing MSDN) was not allowed
> > since IDataReader is an interface (ie, I thought such a
> method could
> > return an object that implemented IDataReader but not an
> instance of
> > an IDataReader object itself since there really wasn't any
> such thing
> > as an IDataReader object).  IOW, it seems that there should be no
> > problem returning an object of, say, type SqlDataReader from this
> > method.
> >
> > I'm obviously not understanding something.  Why is it allowed to
> > return on object of type IDataReader here?
> >
> > Peter

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