1. Active Data Objects Binding ASP.NET Controls to Data
Jim Fawcett
CSE686 – Internet Programming
Summer 2005

2. Support for Data in .Net Connected data access:
Use Connection object and Command to connect a DataReader object to database and read iteratively.
There are two flavors of these objects, Sql--- and OleDb---. The first are tuned to SQL Server and the second can connect to any database the provides drivers, e.g., Access, SQL, Oracle, …
Disconnected data access:
Use a SqlDataSource and GridView or DetailsView or DataList or FormView or Repeater and execute an SQL query or stored procedure.
Use a Connection and Command to connect a DataAdapter to the database and fill a DataSet with the results.
Use a Connection and Command to connect a DataAdaptor to the database and then call Update method of the DataSet.

3. Data Provider Classes

4. ADO Application Structure – ASP.Net 1.1

5. ADO Objects – ASP.Net 1.1

6. ADO Application Structure – ASP.Net 2.0

7. ADO Objects - ASP.Net 2.0

8. Connection Object Methods Properties
Open()
Close()
BeginTransaction()
BeginTransaction().Commit()
Properties
ConnectionString
Windows, SQL, or Forms Authentication
For Windows authentication:
"server=HINDENBURG\\NETSDK;Integrated Security=SSPI; Trusted_Connection=yes; database=pubs“
Also need impersonation code in asp application – see link on CSE686 page.
Database, Datasource, State (open | closed) are readonly properties
You can drag a connection object onto a form
Doesn’t identify a data source

9. Command Object
Used to connect Connection Object to DataReader or a DataAdapter object and execute commands.
Methods
ExecuteNonQuery()
Executes command defined in CommandText property, e.g., UPDATE, DELETE, INSERT, CREATE TABLE, ALTER COLUMN, …
Used for operations that do not return a row of data
ExecuteReader(CommandBehavior)
Returns a DataReader instance attached to the resulting rowset
Assumes you’ve defined a command that implies a query, using CommandText property
ExecuteScalar()
Executes query defined in CommandText and returns the first column of the first row of resulting rowset. Ignores the rest.
Properties
Connection connection string defining Server and database
CommandText Text of SQL query
CommandType StoredProcedure | TableDirect | Text (SQL Query)
Parameters Arguments for stored procedures
Transaction Transaction in which command will execute

10. DataReader Object Supports one-way, forward-only, access to data.
Once data has been read, must be closed and re-created to access data again.
DataReader lasts as long as the connection is open. It can’t be persisted to session.
Methods
Read() Returns one row and advances current row pointer
GetXXX() GetBoolean, GetInt16, GetChars, GetString, GetValue, … different methods for specific XXX types
GetFieldType Returns type of specified column
GetSchemaTable Returns DataTable describing structure of data
NextResult Advances current row pointer
Close() Closes DataReader
Properties
this[string] Specifies column in row by name, returns value
this[int] Specifies column in row by index, returns value
FieldCount Number of columns in current row
Item Value of a column
RecordsAffected Number of rows changed, inserted, or deleted
Normally, a DataReader is returned from a command object, ready to bind to a display control. You get one from the command method ExecuteReader().

11. Data Adapter Object Used to: Methods Properties
extract data from data source and populate tables in a DataSet
Push changes in DataSet back to source
Methods
Fill(DataSet, Table) Loads data from source into DataSet
FillSchema(DataSet, SchemaType)
Update() Returns modified data to source
Properties
SelectCommand SQL Select text
UpdateCommand SQL Update command text
InsertCommand SQL Insert command text
DeleteCommand SQL Delete command text
TableMappings Map for source and DataSet columns

12. DataSet Object Used for Disconnected manipulation of a source’s data.
Read-write, can access tables in any order, as often as you like.
Lasts only as long as the page that created it, unless persisted to session or some other mechanism.
Methods
AcceptChanges Commits pending changes to DataSet
Clear() Empties all Tables
ReadXML(XmlReader) Reads XML data into DataSet
WriteXML(XmlWriter) Writes DataSet data to XML file
HasChanges() boolean returns true if pending changes
AbandonChanges() Reverts to unchanged state
Properties
Tables collection
ds.Tables[tableStr].Rows[3]["Responsible Individual"] = userID;
Relations collection Relationships between Tables in DataSet
Normally, you don’t fill the DataSet, a DataAdapter does that.

13. DataTable Object Holds records from a source per TableMapping
DataSets hold DataTable members in Table Collection.
Properties
Rows Rows collection
Columns Columns collection
TableName Name used in code
DataSet Tables Collection Methods
Tables.Add(TableName)
Tables.Add(DataTable)
Tables.AddRange(TableArray)
DataTable Rows Collection Properties and Methods
Item Value of a specified column
Add(DataRow) method to add a new row
DataTable Columns Collection Properties
ColumnName
DataType

14. SqlDataSource
Used to connect Connection Object to GridView or DetailsView or DropDownList or … objects and execute commands.
Methods
DataBind()
Calls Select(), called by view controls DataBind() method.
Delete(), Insert(), Select(), Update()
Executes command defined DeleteCommand, InsertCommand, SelectCommand, or UpdateCommand
Properties
ConnectionString connection string defining Server and database
Commands DeleteCommand, InsertCommand, SelectCommand, UpdateCommand
CommandTypes DeleteCommandType, … StoredProcedure | Text (SQL Query)
Parameters DeleteParameters, … Arguments for stored procedures

15. Managing Data Coherency
DataSets support disconnect operation. When processing is complete, changes are sent back to the database.
In a multi-user environment, that obviously can cause problems.
Strategies to avoid coherency problems:
Lock records, so others can read but not update.
ADO.Net does not directly provide locks
You can: SqlTransaction t = conn.BeginTransaction(IsolationLevel.Serializable); some code here t.Commit();
Do this in a try, catch block with finalizer that does the commit so you don’t leave a bunch of records locked indefinately if your code throws an exception.
Build the update procedure so that it fails if the affected records where last changed after you read the data. Then go and negotiate.
Allow only one person to update any given area of the data model, partitioned in some reasonable way for the business.

16. References
Pro ASP.NET 2.0 in C# 2005, MacDonald & Szpuszta, Apress, 2006
Programming Microsoft .Net, Jeff Prosise, Microsoft Press, 2002
Professional C#, Robinson et. al., Wrox Press, 2002