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1 17. Data Access ADO.Net Architecture New Features of ADO.NET Visual Studio Visual Studio Wizards and Designers Demonstration: Creating Data Components.

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Presentation on theme: "1 17. Data Access ADO.Net Architecture New Features of ADO.NET Visual Studio Visual Studio Wizards and Designers Demonstration: Creating Data Components."— Presentation transcript:

1 1 17. Data Access ADO.Net Architecture New Features of ADO.NET Visual Studio Visual Studio Wizards and Designers Demonstration: Creating Data Components Lab 17: Accessing Data Using ADO.NET Code Samples

2 2 ADO.NET Architecture What Is ADO.NET? What Is a Connected Environment? What Is a Disconnected Environment? What Is the ADO.NET Object Model? What Is the DataSet Class? What Is the.NET Data Provider?

3 3 What Is ADO.NET? ADO.NET is a data access technology. It provides: A set of classes, interfaces, structures, and enumerations that manage data access from within the.NET Framework An evolutionary, more flexible successor to ADO A system designed for disconnected environments A programming model with advanced XML support

4 4 What Is a Connected Environment? A connected environment is one in which users are constantly connected to a data source Advantages: Environment is easier to secure Concurrency is more easily controlled Data is more likely to be current than in other scenarios Disadvantages: Must have a constant network connection Scalability

5 5 What Is a Disconnected Environment? In a disconnected environment, a subset of data from a central data store can be copied and modified independently, and the changes merged back into the central data store Advantages You can work at any time that is convenient for you, and can connect to a data source at any time to process requests Other users can use the connection A disconnected environment improves the scalability and performance of applications Disadvantages Data is not always up to date Change conflicts can occur and must be resolved

6 6 What Is the ADO.NET Object Model? DataSet DatabaseDatabase.NET Data Provider Connection Transaction Command Parameters DataReader DataAdapter SelectCommand InsertCommand UpdateCommand DeleteCommand DataTableCollection DataTable DataRowCollection DataColumnCollection ConstraintCollection DataRelationCollection XMLXML

7 7 What Is the.NET Data Provider? Manages the connection to a database Executes a query command on the database Exchanges data between the data set and the database Provides efficient access to a stream of read-only data DatabaseDatabase Connection Command DataReader DataAdapter

8 8 Creating an Application That Uses ADO.NET to Access Data How to Specify the Database Connection How to Specify the Database Command How to Create the DataAdapter Object How to Create a DataSet Object How to Bind a DataSet to a DataGrid How to Use the Data Wizards in Visual Studio.NET

9 9 How to Specify the Database Connection Use the Connection object to: Choose the connection type Specify the data source Open the connection to the data source Use the connection string to specify all of the options for your connection to the database, including the account name, database server, and database name string connectionStr Source=localhost; Integrated Security=SSPI; Initial Catalog=northwind";

10 10 How to Specify the Database Command Create a string containing SQL statements Remember that Verbatim strings can make this much easier! Examples of SQL statements: SELECT * FROM Customers SELECT CustomerName FROM Customers SELECT * FROM Customers WHERE Country = 'Mexico' string CustomerName, CompanyName FROM Customers";

11 11 How to Create the DataAdapter Object Data source DataAdapter DataTable DataSet DataAdapter Fill Update Fill

12 12 What Is the DataSet Class? DataSet Constraints Table Column Constraint Rows Row Relations Relation Object Collection Tables Columns DataSets consist of one or more tables and relations Loaded from one or more data adapters Created as you work Loaded from XML Loaded from other DataSets Tables contain columns, constraints, and rows All are collections!

13 13 How to Bind a DataSet to a DataGrid DataGrid dataGrid1 = new DataGrid(); sqlDataAdapter1.Fill(dataSet1, "Customers"); sqlDataAdapter2.Fill(dataSet1, "Orders"); dataGrid1.DataSource = dataSet1; DataGrid dataGrid1 = new DataGrid(); sqlDataAdapter1.Fill(dataSet1, "Customers"); sqlDataAdapter2.Fill(dataSet1, "Orders"); dataGrid1.DataSource = dataSet1; To bind programmatically

14 14 Changing Database Records How to Access Data in a DataSet Object How to Update a Database in ADO.NET How to Create a Database Record How to Update a Database Record How to Delete a Database Record

15 15 DataRow objects How to Access Data in a DataSet Object DataColumn objects DataTable objects DataColumn objects

16 16 How to Update a Database in ADO.NET DataSet Client DataAdapter DatabaseDatabase Server Data Fill Update DeleteCommand UpdateCommand InsertCommand Data DataTable

17 17 How to (Manually) Create a Database Record Create a new row that matches the table schema Add the new row to the dataset Update the database Create a new row that matches the table schema Add the new row to the dataset Update the database DataRow myRow = dataTable.NewRow(); sqlDataAdapter1.Update( dataSet ); dataTable.Rows.Add( myRow );

18 18 How to (Manually) Delete a Database Record Delete the row from the dataset Update the database Accept the changes to the dataset dataTable.Rows[0].Delete(); dataSet.AcceptChanges(); dataAdapter.Update(dataSet);

19 19 Data Reader Data Readers manage the stream of results from a SELECT statement or Stored Procedure Data Readers are read only Data Readers only move forwards through the data – they cannot go backwards No other database operation can be performed while a data reader is open

20 20 Using a DataReader with a SELECT Statement string queryString = "SELECT FirstName, LastName FROM dbo.Employees"; //Create the command objects SqlCommand com = new SqlCommand(queryString, conn); //Call the command's ExecuteReader method SqlDataReader dr = com.ExecuteReader(); //Loop through the datareader to output the employee names while (dr.Read()) { listBox1.Items.Add(dr.GetString(0) + " " + dr.GetString(1)); }

21 21 Using a DataReader to call a Stored Procedure //Create the command object and set its properties SqlCommand com = new SqlCommand(); com.Connection = conn; com.CommandText = "CustOrderHist"; com.CommandType = CommandType.StoredProcedure; //Create the parameter object and add it to the command's collection SqlParameter param = new SqlDbType.NVarChar, 5); param.Value = txtID.Text; com.Parameters.Add(param);

22 22 Creating a Two Tier Application Create the data tier Create a new class library project Create a class to represent a business entity, say customers Add methods that access the database, using ADO.Net Add properties that expose attributes, say name, phone … Create the presentation tier Create a new Windows Application project Add a reference to the above data project Create an object from class Use the objects properties to populate controls on a form Use the objects methods to access the database

23 23 New Features of ADO.NET 2.0 Multiple active result sets One connection can host more than one result set Reduces number of connections on a database Asynchronous operations Begin a data access operation, continue with other tasks, and then later end the original operation Batch updates Update multiple rows in one batch Use the UpdateBatchSize property of the DataAdapter

24 24 Visual Studio Wizards and Designers Data Source Configuration Wizard TableAdapter Configuration Wizard TableAdapter Query Configuration Wizard Preview Data Dialog Box

25 25 Lab 17: Accessing Data Using ADO.NET Exercise 1: Retrieving Data into a Data Set Exercise 2: Updating the Database from a Data Set Exercise 3: Retrieving Data with a Data Reader Exercise 4: Calling a Stored Procedure


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