- DataReader will work with connection oriented Architecture Second Method .
- DataReader is Read-only object i.e., using DataReader we can just read the data from the database, and we cannot perform any operations like Inserting, Updating and deleting records etc.
- DataReader is sequential only object i.e., can read the records one by one only.
- There is no mechanism to move Nth record Directly.
- DataReader is Forward object i.e., it is possible to read current record to next record only. and it is not possible to read the previous record from current record.
- DataReader will use the command object to fetch the data from database.
- Data reader will reserve the connection object i.e., as long as we are working with DataReader connection object cannot be used for other purpose.
Architecture of DataReader:-
S1:-Establishing
the connection to the Server.
S2:-client
sends the request to the server using Command Object for the Required Data
.
.
S3:-Client
request is processed at the server and Query Execution Result is transferred to
the separate Memory allocated to the client at server known as ResultSet.
S4:-Link
is created from the header row of ResultSet DataReader
S5:-
DataReader starts read the data using Read() Method.
S6:-The
data ready by using DataReader can be Displayed in the user Interface
Elements/used for calculation purpose/for any other purpose.
After completion of the
total reading the data either DataReader can be closed or Connection is Closed.
When ResultSet is
Destroyed
- When DataReader is Closed
- When Connection is Closed
Identify the Data Using DataReader:-
In
the above figure if DataReader is reading the first record then we identify the
field data using the index value or field name like.
DR[0] or
DR[“EmpId”] --- 1
DR[1] or
DR[“EName”] --- Sampath
DR[2] or
DR[“Doj”] --- 10/12/2012
DR[3] or
DR[“Salary”] --- 15000
Properties:-
SNo
|
Properties
& options
|
Type
|
Description
|
01
|
FieldCount
|
Int
|
Returns the count of fields
present in the ResultSet
|
02
|
IsClosed
|
Bool
|
Returns true if DataReader is
closed otherwise return false
|
Methods
with DataReader Class:-
SNo
|
Properties
& options
|
Type
|
Description
|
01
|
Close()
|
Void
|
Closes the SQL DataReader object
|
02
|
Read()
|
Bool
|
Advaances the
DataReader to the Next record
Return true of there is another
record otherwise returns false if there is no Recoed.
|
Advantages:-
- Using the DataReader can increase Application performance both by Retrieve data as soon as it is available, and (By Default) storing only one row at a time in memory, reducing system overhead.
- The DataReader is a good choice when retrieve large amounts of data because the data is not cached in Memory.
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