Using keyword “using” in code block

Recently, I have been asked about the alternative way to Dispose objects as we often do in the “finally” block in “Try .. Catch .. Finally” block for connection object. I have seen “using” keyword in some sample codes but I never aware of it does dispose the objects declared as “using”

Example:

using (IDataReader dataReader = _db.ExecuteReader(“GetCategories”))
{
// Processing code
while (dataReader.Read())
{
Category item = new Category(
dataReader.GetInt32(0),
dataReader.GetString(1),
dataReader.GetString(2));
this.cmbCategory.Items.Add(item);
}
}

1. One thing to note is the objects inside the “using” block should implement “IDisposable” interface.
2. Still if we want to cache Exception, we need to inside and for me it seems a little bit redundant if we do the dispose inside the “finally” block as we often do for the connection object