Introduction to ADO.Net

Malek KemmouCEO Arrabeta

kemmou@kemmou.com

bioAdapter.Fill(bio_DataSet);repeater1.DataBind();

CEO Arrabeta (consulting firm based in Casablanca Morocco)Newtelligence Alliance Partner

Senior Consultant and Senior Trainer Solutions Architecture, integration, interoperability

Microsoft Regional Director for Middle East and Africa Ineta MEA Speaker Bureau Speaker at many conferences and events (TechEd, NDC,

MDC, DevDays, DevEssentials …)

Agenda

• Overview of Data Access in .Net• Fetching Data• Processing Data• Data as XML• Tips & Tricks

What is ADO.NET?

• Managed Code (.NET) Data Access Methodology • Complete Integration with the .NET Framework• Improved support for the disconnected business

model• Improved integration with XML• Explicit control of Data Access behaviors

for .NET applications

Introducing ADO.NET

• Part of the .NET framework, ADO.NET was built with the new world of XML, disconnected data, web and HTTP in mind

• Is a rewrite of ADO for the .NET framework–Not a replacement of ADO for COM developers–ADO.NET is a natural evolution of ADO, built

around n-tier development and architected with XML at its core

Overview of Data in .Net

.NET Data Provider.NET Data Provider

DataReaderDataReader

CommandCommandConnectionConnection

SyncSync

Controls,Controls,Design Tools,Design Tools,

Code Generation …Code Generation …

DataSetDataSet

XmlReaderXmlReader

XSL/T, X-Path,XSL/T, X-Path, … …

XMLDataDocumentXMLDataDocument

DataAdapterDataAdapter

Fetching Data

• Connected Model–Create a connection–Open Connection–Execute Commands–Obtain Results–Process Rows–Close Connection–Data Bind

Create & open a Connection

• C#SqlConnection cnn = new SqlConnection(“Data Source = MyServer;

User Id=myUser; password=myPassword”);cnn.Open();

• VB.NetDim cnn as New SqlConnection((“Data Source = MyServer; User

Id=myUser; password=myPassword”)cnn.open

Open a Transaction if needed

• C#SqlTransaction tnx = cnn.BeginTransaction();// do some Data Access and processingIf (somecondition) tnx.Commit();Else tnx.Rollback();• VB.NetDim tnx as SqlTransaction = cnn.BeginTransaction‘ Do some Data Access and processingIf (somecondition) Then

tnx.Commit()Else

tnx.Rollback()End If

Execute Commands

• Various types of commands– Insert, Update, Delete, stored procedure, …

• Optionally transmit parameters

SqlCommand cmd = new SqlCommand("DeleteAccount", cnn);cmd.CommandType = CommandType.StoredProcedure;

SqlParameter param = new SqlParameter("@A_ID",typeof(string));param.Value = accountID;cmd.Parameters.Add(param);

Int32 RowsAffected = cmd.ExecuteNonQuery();

Obtain a Single Value

• Use ExecuteScalar

SqlCommand cmd = new SqlCommand( "Select Balance from Accounts where ” +“AccountID = @A_ID", &cnn);

cmd.Parameters.Add("@A_ID",accountID);

Decimal AccountBalance = (Decimal) cmd.ExecuteScalar();

Process Rows

• Dynamic ProcessingSqlCommand cmd = new SqlCommand("Select Desc, "

+"Amt from Activity where AccountID = @A_ID", cnn);cmd.Parameters.Add("@A_ID",accountID);

SqlDataReader results = cmd.ExecuteReader();

While (results.Read()) {Console.Write("Description: " + results.GetString(0));Console.WriteLine("Amount: " + results.GetDecimal(1));

}

Data Binding(Web Forms)

public void Page_Load(Object sender, EventArgs e) {

// Créer une SqlCommand et obtenir un DataReaderSqlConnection cnn = new SqlConnection("server=localhost;uid=sa;");cnn.Open();SqlCommand cmd = new SqlCommand("Select * from customers", cnn);SqlDataReader results = cmd.ExecuteReader();

// Lier les résulatsActivityList.DataSource = results;ActivityList.DataBind(); }

Demo

Connected DataAccess from a Web Page

Processing Data

• Disconnected Model– Fill DataSet– Navigate the DataSet– Update Changes from DataSet– Data Bind– DataSet can be used as cache

DataSet

• A DataSet is a local buffer of tables, or a collection of disconnected “recordsets”– Keeps track of the relationships between the tables it

contains• DataSets are an in-memory relational store • Exposes a rich programming model

– All data is stored in a local cache– Same performance and semantics regardless of whether

the data is loaded from a database, loaded from XML, or is generated by the application.

• No connection!– (Not directly anyway)

DataSets: Tables

• A DataSet contains a collection of DataTables (the DataTableCollection)– A DataTable represents one table of in-memory data. It

contains a collection of columns (the DataColumnCollection) that represents the table's schema

• A DataTable also contains a collection of rows (the DataRowCollection), representing the data held by the table. It remembers the original state along with current state, tracking the kinds of changes that have occurred.

Fill DataSet from Database

• Use a DataAdapter

SqlCommand selectCommand = new SqlCommand("Select CategoryName from Categories",cnn);

SqlDataAdapter adapter = new SqlDataAdapter();adapter.SelectCommand = selectCommand;

DataSet categories = new DataSet("Categories");adapter.Fill(categories);

Navigate the DataSet

• Navigate the Row Collection of a Table• Obtain Rows as an Array• Use language expressions as “foreach”

foreach(DataRow customer in myDataSet.Tables["Customer"].Rows) {Console.WriteLine("Orders for customer: " + customer["Name"]);foreach(DataRow order in customer.GetChildRows("cust_orders") ) {

Console.Write("\t Order ID = " + order["OrderID"]);Console.WriteLine("Amount = " + order["Amount"]);

}}

Update Changes

SqlDataAdapter adapter = new SqlDataAdapter();

SqlCommand delete = new SqlCommand("DeleteOrder",cnn);delete.CommandType=CommandType.StoredProcedure;delete.Parameters.Add("@OrderID",typeof(Int32)).SourceColumn="OrderID";adapter.DeleteCommand = delete;

SqlCommand insert = new SqlCommand("AddOrder",cnn);insert.CommandType=CommandType.StoredProcedure;insert.Parameters.Add("@OrderID",typeof(Int32)).SourceColumn="OrderID";insert.Parameters.Add("@CustD",typeof(Int32)).SourceColumn="CustomerID";insert.Parameters.Add("@Date",typeof(DateTime)).Value = DateTime.Now;adapter.InsertCommand = insert;

SqlCommand update = new SqlCommand("UpdateOrder",cnn);update.CommandType=CommandType.StoredProcedure;update.Parameters.Add("@OrderID",typeof(Int32)).SourceColumn="OrderID";update.Parameters.Add("@CustD",typeof(Int32)).SourceColumn="CustomerID";adapter.UpdateCommand = update;

adapter.Update(ordersTable);

Winforms DataBinding

SqlCommand cmd = new SqlCommand("GetAccountInfo", cnn);cmd.CommandType=CommandType.StoredProcedure;cmd.Parameters.Add("@A_ID",accountID);

DataSet account = new DataSet;DataAdapter adapter = new DataAdapter(cmd);adapter.Fill(account);

DataGrid accountGrid = new DataGrid();accountGrid.SetDataBinding(myDataSet, "AccountList");

Demo

A Simple WinForm Working with Data

ADO .NET & XML

• DataSets and XML– Load/Save XML Data to/From DataSet– Schema can be loaded/saved as XSD– Schema can be inferred from XML Data

Loading XML

DataSet ds = new DataSet();ds.ReadXml("inventory.xml");

DataTable inventory = ds.Tables["Inventory"];DataRow row = inventory.NewRow();row["TitleID"]=1;row["Quantity"]=25;inventory.Rows.Add(row);

ds.WriteXml("updatedinventory.xml");

Load Schema from XSD

myDataSet.ReadXmlSchema(schemaFile);

– Complex Types converted to tables– Nested Complex Types converted to child

tables– Keys/Constraints converted into unique

constraints– Foreign Key Constraints inferred

Inferred Schema

• If no schema is defined before calling DataSet.ReadXml(), schema is inferred from data

• General Rules– An element becomes a table if :

• It is repetitive within its parent or it contains more than one simple content

• …Otherwise, it becomes a column

– Attributes become columns– Relations are created for nested tables

• Hidden columns are created for the keys

• Useful for dynamic data binding

Demo

DataSets and XML

X/Path And XSL/TOver DataSet

XmlDataDocument xmlData = new XmlDataDocument(po);

// Requête X/PathXmlNodeList nodes = xmlData.SelectNodes("//Item[@qty>100]");foreach(XmlNode node in nodes) { DataRow row = xmlData.GetRowFromElement((XmlElement)node); row.Delete();}

// Transformation XSLTXslTransform xsltransform = new XslTransform();xsltransform.Load("po.xsl");XmlReader xReader = xsltransform.Transform(xmlData, null);

Tips & Tricks

• Auto generate Commands for updating DataSet

• Refreshing DataSet data

• Managing and processing errors when updating a DataSet

• Working with row versions and changes

• Passing null values

• Guarantee connection closes when DataReader is finished

• Inserting primary keys

Auto Generate Commandsfor Updating DataSet

• Use CommandBuilder

SqlDataAdapter sda = new SqlDataAdapter(“select x, y, z from table1”,cnn);

SqlCommandBuilder scb = new SqlCommandBuilder(sda);sda.UpdateCommand = scb.GetUpdateCommand();sda.InsertCommand = scb.GetInsertCommand();sda.DeleteCommand = scb.GetDeleteCommand();

sda.Update(ds);

Refreshing DataSet Data

• Fill data with the Fill method of the AdaptermyAdapter1.fill(dataSet12);

• Process data.• Before Updating, use :

DataSet dataSetTemp = new DataSet();myAdapter1.fill(dataSetTemp);dataSet12.Merge(dataSetTemp, true);

Managing and Processing ErrorsWhen updating DataSet

• DataAdapter.ContinueUpdateOnError– Default is False; setting to True allows all updates to complete even if

updates on certain rows generate errors• DataTable.GetErrors()

– Returns array of DataRow objects that represent rows whose updates failed

• DataRow.RowError– Returns a string with a general error message that applies to the entire

row• DataRow.GetColumnsInError()

– Returns array of DataColumn objects that contributed to error• DataRow.GetColumnError(x)

– Returns string description of the error itself– x is column ordinal, name, or DataColumn object

Working with Row versionsand changes

• Item(x)– Allows you to examine the value of column x, where x is column’s

ordinal or name• Item(x, version)

– Allows you to examine the value of a specific version of column x (DataRowVersion.Current, .Default, .Original, or .Proposed)

• BeginEdit(), EndEdit() – In conjunction with .Items(x), allows you to modify column values in the

row• CancelEdit()

– Abandons pending changes to an edited row• RowState

– DataRowState.Added, .Deleted, .Detached, .Modified, or .Unchanged

Passing null values

• Use DBNull.Value

SqlParameter param = new SqlParameter();param.Value = DBNull.value;

Guarantee connection closeswhen DataReader finishes

• Use CommandBehavior.CloseConnection

private DataReader getCategories() {SqlCommand cmd = new SqlCommand( "Select * from Categories, cnn);DataReader results = cmd.ExecuteReader(CommandBehavior.CloseConnection);

return results;}

Inserting Primary Keys• Use Guids as Primary Keys

• Can be generated on the client• Guarantees to be unique• Doesn’t change when updated on the server

– No problem on child tables

Summary• ADO.Net has tailored objects

– .NET Data Providers for connected access• Executing commands• DataReader

– DataSet for disconnected access, user interaction and caching• ADO.Net and XML are made for each other

Questions

• I will post session content on my blog :

http://www.malekkemmou.ma