which is better, closing a datareader or setting it to null?

I would like to know the advantage and disadvantage of the following operation

shall i bet开发者_JAVA百科ter set the datareader to null than calling the close method. If this is good what are the advantages, else what is the problem in using so?.

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You should use the using statement instead:

using (var reader = sqlCommand.ExecuteReader())
{
  // do stuff
}

That way, you are sure that the reader is closed (disposed), even if an exception was raised in the "do stuff" block.

For a complete example, see this MSDN page.

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Update (regarding your comment):

The using statement is in fact nothing else than a try-finally block to ensure that the reader is disposed (closed) in every case. E.g. the above code is equivalent to this:

SqlDataReader reader = null;
try
{
  reader = sqlCommand.ExecuteReader();
}
finally
{
  reader.Dispose(); // closes the reader
}