What is the difference between data adapter and data reader?
Please see DataReader, DataAdapter & DataSet - When to use? :
ADO.NET provides two central Data
Access Components. The excellent thing
is that, they are common across all
Databases, be it SQL Server or other
competitive databases. Its only the
namespace to be used, that differs,
while using a Database other than SQL
Server.
A DataReader is an object returned from the ExecuteReader method of a DbCommand object. It is a forward-only cursor over the rows in the each result set. Using a DataReader, you can access each column of the result set, read all rows of the set, and advance to the next result set if there are more than one.
A DataAdapter is an object that contains four DbCommand objects: one each for SELECT, INSERT, DELETE and UPDATE commands. It mediates between these commands and a DataSet though the Fill and Update methods.
Data Reader is an object used in connected Environment.
Data Adapter is an object used in Disconnected environment using Dataset.
DataReader is a faster way to retrieve the records from the DB. DataReader reads the column. DataReader demands live connection but DataAdapter needs disconnected approach.
Here is a nice article on the above topic:
Difference Between DataReader, DataSet, DataAdapter and DataTable in C#
Key differences in simple terms:
Unlike classic ADO, which was primarily designed for tightly coupled client/server systems,ADO.NET was built with the disconnected world in mind, using DataSets/DataAdapter.
DataAdapter follows connectionless-oriented architecture which simply means you need not necessarily be connected to a data-source whereas DataReader is a connection-oriented architecture which means it needs an active connection to a data-source for it to operate.
DataAdapter is an intermediate layer/ middleware which acts a bridge between the DataSet and a Database whereas DataReader provides forward-only, read-only access to data using a server-side cursor (simply put it is ued to read the data).
Using DataSet we can manipulate and update a DataSet's contents while disconnected from the Datasource and send any modified data back for processing using a related DataAdapter whereas DataReader can only read data from a Database & cannot modify it.
DataAdapter object is used to read the data from database and populates that data to DataSet whereas DataReader simply reads the data using the Read() method.
DataAdapter is comparatively slower whereas using DataReader can increase application performance both by retrieving data as soon as it is available, and (by default) storing only one row at a time in memory, reducing system overhead.
Data reader is an object through which you can read a sequential stream of data. it's a forward only data wherein you cannot go back to read previous data.
data set and data adapter object help us to work in disconnected mode. data set is an in cache memory representation of tables. the data is filled from the data source to the data set thro' the data adapter. once the table in the dataset is modified, the changes are broadcast to the database back thro; the data adapter.
DataAdapter
DataAdapter will acts as a Bridge between DataSet and database. This dataadapter object is used to read the data from database and bind that data to dataset. Dataadapter is a disconnected oriented architecture.
DataReader
DataReader is used to read the data from database and it is a read and forward only connection oriented architecture during fetch the data from database. DataReader will fetch the data very fast when compared with dataset. Generally we will use ExecuteReader object to bind data to datareader
Related
Is it possible to exist the connection between the extensive use of asp:SqlDataSource and a lot of 3306 ports in time wait status?
Is it true that the asp:sqldatasource closes the connection automatically? if does not, how to close the connection made by a slqdatasource?
Thanks in advance,
Firmino
Try <asp:SqlDataSource DataSourceMode="DataSet" />.
From MSDN:
The data retrieval mode identifies how a SqlDataSource control retrieves data from the underlying database.
When the DataSourceMode property is set to the DataSet value, data is loaded into a DataSet object and stored in memory on the server. This enables scenarios where user interface controls, such as GridView, offer sorting, filtering, and paging capabilities.
When the DataSourceMode property is set to the DataReader value, data is retrieved by a IDataReader object, which is a forward-only, read-only cursor. The specific type of the IDataReader object depends on the NET data provider that the SqlDataSource uses, which is identified by the ProviderName property. By default, the SqlDataSource control uses the provider for Microsoft SQL Server, the System.Data.SqlClient, and the data reader is a SqlDataReader object.
DataReader requires open connection to operate - it returns data directly from DB. In constrast DataSet loads data from DB to memory so connection are opened only for actual read / update / insert / delete and can be closed (=returned to pool) afterwards.
Source: SqlDataSource.DataSourceMode
I used to work in VB.net and used Dataset's all the time when working with ADO, but now i'm Working in C# and the Research is showing me a lot of Recordsets.
Are they the same thing?
If no what is the difference?
Datasets vs RecordSets
Essentially it is to do with how it fetches the data and allows you to intereact with it, recordsets would typically only allow you to fetch data from one table at a time (with default settings) whereas datasets can retrieve the entire set of data. there is more information at that link
Dataset is a connectionless data holder whereas RecordSet is connection oriented Data holder.Though DataSet you can refer more than 1 table at a time, but in the case of Recordset only 1 table is processed at a time. Through Dataset you can process more than 1 record,but in case of recordset recordset you have to make travesel to each record and after that you can make processing.
a direct quote backing up what i said
Difference between ADO.NET Dataset and ADO Recordset?
ADO.NET is an object-oriented set of libraries that allows you to interact with data sources.
http://www.job4india.in/interview-questions/net-interview-questions
ADO :-
1.It is a COM based library.
2.Classic ADO requires active connection with the data store.
3.Locking feature is available.
4.Data is stored in binary format.
5.XML integration is not possible.
ADO.NET :-
1.It is a CLR based library.
2.ADO.NET architecture works while the data store is disconnected.
3.Locking feature is not available.
4.Data is stored in XML.
Read More :- http://www.job4india.in/net-interview-questions/what-difference-between-ado-and-adonet
No, the DataSet class (System.Data namespace) has the same name in C#. I'm not familiar with anything called recordset in ADO.NET (whereas I am with DataSet). Could you post some examples?
When using a Class to get one row of Data from the Database what is best to use:
A DataSet?
A Reader and do what store the data in a Structure?
What else?
Thanks for your time, Nathan
A DataReader is always your best choice--provided that it is compatible with your usage. DataReaders are very fast, efficient, and lightweight--but they carry the requirement that you maintain an active/open db connection for their lifecycle, this means they can't be marshalled across AppDomains (or across webservices, etc).
DataSets are actually populated by DataReaders--they are eager-loaded (all data is populated before any is accessed) and are therefore less performant, but they have the added benefit of being serializable (they're essentially just a DTO) and that means they're easy to carry across AppDomains or webservices.
The difference is sometimes summed up by saying "DataReaders are ideal for ADO.NET ONLINE (implying that it's fine to keep the db connection open) whereas DataSets are ideal for ADO.NET OFFLINE (where the consumer can't necessarily connect directly to the database).
DataAdapter (which fills a DataSet) uses a DataReader to do so.
So, DataReader is always more lightweight and easier to use than a DataAdapter. DataSets and DataTables always have a huge overhead in terms of memory usage. Makes no difference if you are fetching a single row, but makes a huge difference for bigger result sets.
If you are fetching a fixed number of items, in MS SQL Server, output variables from a stored proc (or parameterized command) usually perform best.
if you use a reader you must have a open connection to your database generally a DataReader is used for fetch a combo or dataGrid, but if you want to stock your data in memory and you close our data base connexion you must use Datatable
Note : excuse my english level
If you just want read-only access to the data, then go with a raw DataReader; it's the fasted and most lightweight data access method.
However, if you intend to alter the data and save back to the database, then I would recommend using a DataAdapter and a DataSet (even a typed DataSet) because the DataSet class takes care of tracking changes, additions and deletions to the set which makes saves much easier. Additionally, if you have multiple tables in the dataset, you can model the referential constraints between them in the dataset.
I just saw this topic: Datatable vs Dataset
but it didn't solve my doubt .. Let me explain better, I was doing connection with database and needed to show the results in a GridView. (I used RecordSet when I worked with VB6 while ago and DataSet is pretty similar to it so was much easier to use DataSet.)
Then a guy told me DataSet wasn't the best method to do ..
So, should I 'learn' DataReader or keep using DataSet ? DataTable ?
What are the pros/cons ?
That is essentially: "which is better: a bucket or a hose?"
A DataSet is the bucket here; it allows you to carry around a disconnected set of data and work with it - but you will incur the cost of carrying the bucket (so best to keep it to a size you are comfortable with).
A data-reader is the hose: it provides one-way/once-only access to data as it flies past you; you don't have to carry all of the available water at once, but it needs to be connected to the tap/database.
And in the same way that you can fill a bucket with a hose, you can fill the DataSet with the data-reader.
The point I'm trying to make is that they do different things...
I don't personally use DataSet very often - but some people love them. I do, however, make use of data-readers for BLOB access etc.
It depends on your needs. One of the most important differences is that a DataReader will retain an open connection to your database until you're done with it while a DataSet will be an in-memory object. If you bind a control to a DataReader then it's still open. In addition, a DataReader is a forward only approach to reading data that can't be manipulated. With a DataSet you can move back and forth and manipulate the data as you see fit.
Some additional features: DataSets can be serialized and represented in XML and, therefore, easily passed around to other tiers. DataReaders can't be serialized.
On the other hand if you have a large amount of rows to read from the database that you hand off to some process for a business rule a DataReader may make more sense rather than loading a DataSet with all the rows, taking up memory and possibly affecting scalability.
Here's a link that's a little dated but still useful: Contrasting the ADO.NET DataReader and DataSet.
Further to Marc's point: you can use a DataSet with no database at all.
You can fill it from an XML file, or just from a program. Fill it with rows from one database, then turn around and write it out to a different database.
A DataSet is a totally in-memory representation of a relational schema. Whether or not you ever use it with an actual relational database is up to you.
Different needs, different solutions.
As you said, dataset is most similar to VB6 Recordset. That is, pull down the data you need, pass it around, do with it what you will. Oh, and then eventually get rid of it when you're done.
Datareader is more limited, but it gives MUCH better performance when all you need is to read through the data once. For instance, if you're filling a grid yourself - i.e. pull the data, run through it, for each row populate the grid, then throw out the data - datareader is much better than dataset. On the other hand, dont even try using datareader if you have any intention of updating the data...
So, yes, learn it - but only use it when appropriate. Dataset gives you much more flexibility.
DataReader vs Dataset
1) - DataReader is designed in the connection-oriented architecture
- DataSet is designed in the disconnected architecture
2) - DataReader gives forward-only access to the data
- DataSet gives scrollable navigation to the data
3) - DataReader is read-only we can’t make changes to the data present under it
- DataSet is updatable we can make changes to the data present under it and send those changes back to the data source
4) - DataReader does not provide options like searching and sorting of data
- DataSet provides options like searching and sorting of data
To answer your second question - Yes, you should learn about DataReaders. If anything, so you understand how to use them.
I think you're better of in this situation using DataSets - since you're doing data binding and all (I'm thinking CPU cycles vs Human effort).
As to which one will give a better performance. It very much depends on your situation. For example, if you're editing the data you're binding and batching up the changes then you will be better off with DataSets
DataReader is used to retrieve read-only and forward-only data from a database. It read only one row at a time and read only forward, cannot read backward/random. DataReader cannot update/manipulate data back to database. It retrieve data from single table. As it is connected architecture, data is available as long as the connection exists.
DataSet is in-memory tables. It is disconnected architecture, automatically opens the connection and retrieve the data into memory, closes the connection when done. It fetches all the data at a time from the datasource to its memory. DataSet helps to fetch data from multiple tables and it can fetch back/forth/randomly.DataSet can update/insert/manipulate data.
I am just learning C# through Visual Studio 2008?
I was wondering what exactly is the correlation between dabases, datasets and binding sources?
As well, what is the function of the table adapter?
At a super high level:
Database -- stores raw data
DataSet -- a .NET object that can be used to read, insert, update and delete data in a database
BindingSource -- a .NET object that can be used for Data Binding for a control. The BindingSource could point to a DataSet, in which case the control would display and edit that data
TableAdapter -- Maps data from a database table into a DataSet
There is a lot more to all of these, and understanding the way ADO.NET is architected can take a bit of time. Good luck!
A DataSet is usually used to hold a result from the database in memory, i.e. it contains a DataTable object. The DataSet and DataTable objects themselfs are independent of the database, so the result doesn't have to come from a database. The DataSet can contain several DataTables, and you can even define relations between them. It's like a mini database in memory.
A binding source is any object that can provide a list of objects with properties. A DataSet or a DataTable can do that, but it could basically be any kind of list containing objects that has properties.
A TableAdapter is used to read data from a DataReader provided by a Command object, and put the data in a DataTable object.
The dataset is a (partial) in-memory representation of a database. Tables or Views in the datatbase are represented as datatables in a dataset. The dataadapter is the link between the database and the dataset. Once the adapter has loaded the data into the dataset, the physical connection to the dataset is disposed. This is why it's called a disconnected data-model.