Why SqlDataReader is Not Inherit

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In The .NET Framework

SqlDataReader class which property have that why i can't Inherit it

or can we make class with out seal Keyword That is not inherited in our application like SqlDataReader Class That is also Public class

C#

// Summary:
    //     Provides a way of reading a forward-only stream of rows from a SQL Server
    //     database. This class cannot be inherited.
    public class SqlDataReader : DbDataReader, IDataReader, IDisposable, IDataRecord
     
     {
      //
      //
      //
      //
      .
      .   
      .
      .
      .

     }

Posted 13-Oct-11 22:54pm

anil_bang0011

Updated 13-Oct-11 23:26pm

Mehdi Gholam

v2

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3 solutions

Solution 2

refer msdn explanation

http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqldatareader.aspx[^]

Posted 13-Oct-11 23:28pm

devildx2050

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BobJanova · Accepted Answer · 2011-10-13T23:48:00

Solution 3

You can create a class that can't be inherited if it has no constructors that a subclass can see (i.e. nothing protected or public). You can create one that can't be inherited outside the assembly it resides in by having only internal (or protected internal) constructors. I would say, though, that if your intention is to make a class non-inheritable, you should mark it as sealed (and Microsoft should have done so here unless it is internally inheritable, which it probably is).

Posted 13-Oct-11 23:48pm

BobJanova

Comments

anil_bang0011 14-Oct-11 11:35am

ok if we use out side of assembly i think all is is not inherited even they are public

but in case SqlDataReader we use with in assembly
and we can't access in sub class
in C# by default create constructors

public class MyClass
{

}
class Program :MyClass
{
static void Main(string[] args)
{

}
}

how can i avoid MyClass is not inherited in Program class

BobJanova 14-Oct-11 12:54pm

This is an English language site >_>

To make MyClass non-inheritable, you should mark it sealed.

OriginalGriff · Accepted Answer · 2011-10-13T23:03:00

Solution 1

The SqlDataReader class is not sealed, but you cannot inherit from it as it is not a class you can instantiate. I.e. you cannot say:

C#

SqlDataReader sdr = new SqlDataReader();

If you think about it, it makes a lot of sense. A data reader is only used to read all the information returned from a SQL Command execution, so creating a new instance of it completely useless - it has no SQL results to read through. So, the only way you can get an instance is by requesting it from an SQLCommand by using the ExecuteReader method.

So, if you can't create an instance, why would it be possible to inherit from it? You can't create the inherited instance at all - you cannot "upgrade" a class to a derived version, as the framework would have to "invent" all the missing information.

What are you trying to achieve, that you think this would be a good idea?

Posted 13-Oct-11 23:03pm

OriginalGriff

Comments

anil_bang0011 14-Oct-11 7:59am

I did not going to achieve anything .. i just read the framework that why i have a Question

and SqlDataReader sdr = new SqlDataReader();
is also provide by the Sealed Class that is we always done with String

i just ask just which property make its Un - Inherited
and nothing more i want to .....

Thanks

OriginalGriff 14-Oct-11 8:45am

Good for you! There is technically no property that makes it un-inheritable; it is the specific lack of an accessible constructor that prevents it - unlike a string, which is a sealed class and nothing can inherit from it. The chances are that in practice the SQLDataReader constructors are declared as internal, so that it can be inherited from within same namespace. Why? It could be as simple as Microsoft forgot to mark it as sealed, or it could be that there are "hidden" classes that internally inherit from it.
If you want to do the same, I would strongly suggest using sealed instead if you can, as it make it more obvious to anyone trying to use your class.

anil_bang0011 14-Oct-11 11:23am

Hi Thanks alot's your answer

Thanks :) :)

anil_bang0011 14-Oct-11 11:37am

if you saying Microsoft forgot to mark is sealed .. I think its a good Joke

public class MyClass
{

}
class Program :MyClass
{
static void Main(string[] args)
{

}
}

how can i avoid MyClass is not inherited in Program class

OriginalGriff 14-Oct-11 12:08pm

Sorry? That doesn't make a lot of sense. You can inherit from MyClass in Program - it will compile cleanly, and work perfectly well.
Strange thing to do, but it will work.