ADO.NET Data Access with Microsoft .NET

Transcription

ADO.NET
Data Access with Microsoft .NET
Andreas Schabus
Academic Relations
Microsoft Österreich GmbH
andreas.schabus@microsoft.com
http://blogs.msdn.com/msdnat
Session Targets
• What is ADO.NET and how does it work?
• What are the differences to traditional, connected
data access methods?
• What are DataReaders and DataSets and when to use
what?
The Role Of ADO.NET
• Data access framework
– Database independent
– All types of applications
– Successor of class ADO
• Developed in .NET
– Language independent
– Application type independent
• Database independent
Changing Requirements
Different application types
High scale
web
• High scale web
– Always connected (?)
– Extreme performance
• Offline Smart Client
– Definitely not connected
Offline
Smart Client
Connected vs. Disconnected
• Disconnected model
– Save resources
– Enable offline
• Connected model
– Increase performance
– Easier programming model
• Solution: compromise
– As few connections as possible
– Offline object / programming model
Understanding fundamental classes
ADO.NET ARCHITECTURE
The ADO.NET Model
• Get your data
– Connect and retrieve
– Static forward / read only cursor
– No locking
• Work disconnected
– XML support
– Similar to record set
• Update your data
– Connect and execute SQL
ADO.NET Architecture
• Managed Provider
– Access to data source
– Data source classes
• Connection
• Command, Parameter
• DataReader
• Offline classes
– DataTable
– DataSet (n DataTables)
Application
Windows Forms, Web Forms,
Web Services
ADO .NET
Klassen
Dataset
Data
Reader
Managed Provider
SQL Server … OLE DB
Data
Source
ADO.NET Object Model
Connection
Command
DataSet
DataTable
Parameter
DataColumn
DataReader
DataRow
Transaction
DataAdapter
.NET Data Provider
Constraint
DataRelation
Database Support
• Basically independent
– System.Data
– System.Data.Common
• Data providers out-of-the-box
–
–
–
–
System.Data.SqlClient
System.Data.OracleClient
System.Data.Odbc
System.Data.OleDb
• Custom providers
Connection Class
• Base interfaces / classes
– IDbConnection
• Primary tasks
– Connect to database
– Start transactions
SqlConnection cn;
cn = new SqlConnection("server=localhost;database=pubs");
cn.Open()
'... Some tasks...
cn.Close()
Commands And Parameters
• Command base interface
– IDbCommand
• Primary tasks
– Encapsulate SQL command
• Text or Stored Procedure
– Manage query-parameters
– Execute SQL command
string strSQL = "SELECT * FROM titles"
SqlCommand cmd = new SqlCommand(strSQL, Conn)
SqlDataReader reader = cmd.ExecuteReader()
Commands And Parameters
• Parameter base interface
– IDataParameter
• Primary tasks
– Parse & verify parameter
– Convert to database type
string strSQL = "SELECT * FROM titles WHERE name LIKE @val“;
SqlCommand cmd = new SqlCommand(strSQL, Conn);
cmd.Parameters.Add("@val", SqlTypes.VarChar, 20);
cmd.Parameters["@val„].Value = "Programming%„;
SqlDataReader reader = cmd.ExecuteReader();
DataReader Class
• Base interface
– IDataReader
• Primary task
– Read data from result-set
– Forward-only, read-only  performance
SqlDataReader rdr As SqlDataReader = cmd.ExecuteReader();
While(rdr.Read()){
Console.WriteLine(rdr["OrderID“]);
Console.WriteLine(rdr[1]);
Console.WriteLine(rdr.GetString[2]);
}
rdr.Close();
Simple data access
DataTables and DataSets
THE OFFLINE MODEL
DataTable Class
• In-memory snapshot
– Single table
– Scrollable, updateable
– Data source independant
• Schema information
– Columns, column-types
– Rule constraints
• User data
– Snapshot of database data
– DataRow class
DataSet Class
• Data container, too
– Multiple tables
– Relations between tables
• Schema information
– List of tables
– Relations between tables
• DataRelation
• Verified offline
• Enables navigation
Function of the DataAdapter
DataSet
• Datencontainer
• verwendet intern XML
Mapping:
DataReader  DataSet
DataAdapter
SelectCommand
Connection
InsertCommand
UpdateCommand
DeleteCommand
DataAdapter Class
• Base interface, class
– IDataAdapter
– DataAdapter
• Primary tasks
– Execute SQL (read & update)
– Result-set  DataTable / DataSet
SqlConnection cn = new SqlConnection("server=localhost;...")
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM titles", cn)
DataSet ds = new DataSet();
da.Fill(ds, "Titles")
Processing Steps (1/2)
• Define Command
– Eventually create command-object
• Create DataAdapter
– Requires command & connection
• Create & fill DataTable / DataSet
– Instantiate DataSet
– Call DataAdapter.Fill()
– Optional – DataAdapter.FillSchema()
Processing Steps (2/2)
• Change data offline
– Add rows (DataTable.NewRow())
– Delete rows (DataRow.Delete())
– Change rows
Row["Fieldname"] = value
• Update in database
– Call DataAdapter.Update()
– All changes in DataTable / DataSet
– Changed records, only
DataAdapter und DataSets
Read via Fill() & FillSchema()
SqlConnection cn = new SqlConnection("server=localhost;...");
SqlAdapter da = new SqlDataAdapter("SELECT * FROM titles", cn);
da.Fill(ds, "Titles");
Change existing rows
DataRow row;
ds.Tables["Titles„].Rows(0)["name„] = "Neuer Name„;
row = ds.Tables["Titles„].Rows(2)
row.BeginEdit()
row["name„] = "Advanced ADO.NET"
row["Verlag„] = "Microsoft Press"
row.EndEdit()
'or row.CancelEdit()
DataAdapter und DataSets
Add new rows
DataRow newRow;
newRow = ds.Tables["titles„].NewRow();
newRow["name„] = "Applied ADO.NET Programming;
newRow["Verlag„] = "Microsoft Press„;
ds.Tables.Rows.Add(newRow)
Delete existing rows
string filter = "PubDate <= '1/1/1995'„;
DataRow[] delRow();
delRow = ds.Tables["titles„].Select(filter);
foreach( DataRow dr in delRow){
dr.Delete()
]
DataAdapter and DataSets
• Creating necessary commands
– Via Designer (empfohlen)
– Dynamically: SqlCommandBuilder
• Via Get????Command() method
• Primary key in DataTable (FillSchema() !!)
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM titles", cn);
SqlCommandBuilder cmdBuilder;
cmdBuilder = new SqlCommandBuilder(da);
• Execute the update
da.Update(ds)
DataView Class
• Like database view
– But offline
– On DataTable contents
• Primary tasks
– Filtering, sorting
– Intended for binding to controls!!
'...
da.Fill(ds, "Titles");
DataView dv = new DataView(ds.Tables["Titles"]);
DataView dv = ds.Tables["Titles"].DefaultView;
Now you know…
• …what ADO.NET is and it works.
• …what are the differences between connected and
disconnected data access.
• …what DataReaders and DataSets are and how the
can be used?
Bibliographie
CodePlex. (21.02.2008). Microsoft SQL Server Community & Samples. Retrieved
March 09, 2008, from http://codeplex.com/SqlServerSamples
DevASP.Bet. Retrieved March 09, 2008, from
http://www.devasp.net/net/search/display/category74707.html
Microsoft Corporation. .NET Framework Developer's Guide: ADO.NET.
Retrieved March 09, 2008, from http://msdn2.microsoft.com/enus/library/e80y5yhx.aspx
Microsoft Corporation. Gewusst wie: Binden eines Windows FormsSteuerelements an ein Factoryobjekt. Retrieved March 09, 2008, from
http://msdn2.microsoft.com/de-de/library/at23yw2h(vs.80).aspx
Mössenböck, H., Beer, W., Prähofer, H., & Wöß, A. (09.02.2007). Application
Development with C# and .NET. Retrieved March 06, 2008, from
http://dotnet.jku.at/courses/dotnet/

ADO.NET Data Access with Microsoft .NET

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