Using Stored Procedures in Conjunction with the SqlDataAdapter

ncapsulating data update logic in stored procedures is an excellent way to improve the manageability, scalability, and security of your database-driven applications. There are many advantages to incorporating stored procedures into your application logic including:

  • Shared application logic among various client applications
  • Faster execution
  • Reduced network traffic
  • Improved database security

This article will show you how to use stored procedures in conjunction with the SqlDataAdapter in order to fill and update data contained in a DataSet.

Creating a Stored Procedure
Creating a stored procedure is a fairly straightforward process which you can complete inside the Visual Studio .NET IDE. Open Visual Studio .NET and navigate to the Pubs database node in the Server Explorer window and expand the node. You should see a Stored Procedures node (see Figure 1). Right-click on the Stored Procedures node to launch a popup menu. Select the option to create a new stored procedure.

Fill a DataSet using a Stored Procedure
In order to fill a DataSet with the publisher information, you can use a SqlDataAdapter as a broker between the SQL Server and the DataSet. The Fill method of the SqlDataAdapter retrieves the data from the database and populates the DataSet. Before you can execute the Fill method of the SqlDataAdapter, you must execute its SelectCommand property to a valid SqlCommand object. This SelectCommand is responsible for executing the T-SQL statement that returns the result set, which in turn fills the DataSet object.

In order to demonstrate how to execute a stored procedure to fill a DataSet, create a new Windows Application project in Visual Studio. Add a class to the project and rename it Publishers. Add an Imports statement above the class definition to import the SqlClient namespace. Declare a private, class-level instance of each of the following classes: SqlConnection, SqlDataAdapter, SqlCommand, and DataSet.

   Imports System.Data.SqlClient   Public Class Publishers       Private cnPubs As SqlConnection       Private daPubs As SqlDataAdapter       Private cmdSelPubInfo As          SqlCommand       Private dsPubs As DataSet   End Class

Create a class constructor (Sub New)

In the body of the constructor, instantiate the Connection object and pass in the connection string information. Instantiate the SELECT command and set the Connection, CommandType, and CommandText properties. Instantiate the DataAdapter and set its SelectCommand property to the cmdSelPubInfo object. Finally, instantiate the DataSet object, which will hold the result set returned from the database.

   Public Sub New()     'Connection     Dim strCon As String     strCon = "server=localhost;"     strCon += _       "integrated security=true;"     strCon += "database=pubs"     cnPubs = New SqlConnection(strCon)     'select command     cmdSelPubInfo = New SqlCommand()     cmdSelPubInfo.Connection = cnPubs     cmdSelPubInfo.CommandType = _       CommandType.StoredProcedure     cmdSelPubInfo.CommandText = _       "up_GetPubInfo"     ' DataApapter     daPubs = New SqlDataAdapter()     daPubs.SelectCommand = _       cmdSelPubInfo     'Dataset     dsPubs = New DataSet()   End Sub
Note: This assumes you have a local instance of SQL Server and are logged on with a trusted connection.

Create a function procedure called GetPubInfo in the class that takes no input parameters and returns a DataSet to the caller. In the body of the function, use the Fill method of the DataAdapter to fill the DataSet, then return it to the caller.

   Public Function GetPubInfo() As _       DataSet     daPubs.Fill(dsPubs)     Return dsPubs   End Function
Note: Error handling has been omitted for clarity.

The Fill method of the DataAdapter will implicitly open the connection if it is closed and close it after the data is retrieved. If you explicitly open the connection, however, the DataAdapter will not close it.

To test the method, place a DataGrid on Form1. Switch to the Code Editor window and declare a private class level instance of the Publishers class and the DataSet class after the Inherits statement.

   Public Class Form1       Inherits System.Windows.Forms.Form       Private objPublishers As          Publishers       Private dsPubInfo As DataSet

In the Forms constructor code, instantiate a new instance of the Publishers class. Set dsPubInfo to the DataSet returned by calling the GetPubInfo method of the Publishers class. Set the DataSource property of the DataGrid to the first (and only) table in the dsPubInfo tables collection.

   Public Sub New()       MyBase.New()       'This call is required by the        'Windows Form Designer.       InitializeComponent()       'Add any initialization after        'the InitializeComponent()        'call       objPublishers = New _           Publishers()       dsPubInfo = _           objPublishers.GetPubInfo()       Me.DataGrid1.DataSource = _           dsPubInfo.Tables(0)   End Sub

Run the application in the debugger and verify that the results are displayed in the grid.

Update Data with a Stored Procedure
In addition to the SelectCommand property, the SqlDataAdapter object includes the UpdateCommand, InsertCommand, and the DeleteCommand properties. The Update method of the SqlDataAdapter will call the appropriate SqlCommand object for each updated, inserted, or deleted DataRow in the DataTable passed with the update call. When updating data, input parameters pass the values of the updated fields to the stored procedure.

The SqlParameter class encapsulates properties and methods for working with parameters. The SqlParameter class includes properties such as the ParameterName, SqlDBType, Direction, Size, Value, SourceColumn, and SourceVersion. The ParameterName, SqlDBType, Direction, and Size properties are set to match the parameter definition in the stored procedure. For example, the following code creates a parameter object that matches the @pub_id parameter in the up_UpdatePubInfo stored procedure created previously.

   Dim UpdParam As New      SqlParameter("@pub_id",     SqlDbType.Char, 4)

In this case, an overloaded constructor of the SqlParameter class sets the appropriate properties. Although the Direction property has not been explicitly set, Input is the default value. If the parameter direction is InputOutput, Output, or ReturnValue, you must explicitly set the direction. For example, the following code explicitly sets the Direction property of a SqlParameter object.

The SourceColumn property maps a DataColumn from the DataTable passed in when you call the Update method of the SqlDataAdapter object. This mapping allows the implicit loading of the SqlParameter’s Value property from the DataTable during updates. If you do not set the SourceColumn parameter, you must explicitly set the Value property of the SqlParameter object.

The SourceVersion property defaults to a value of Current, which is the current value of the field in the DataRow and is the value that you intend to update in your database. You can also set the SourceVersion of a SqlParameter object to a value of Original, which is the value of the field when the DataTable was originally loaded from the database. Passing both of these values to a stored procedure allows for concurrency checking before the data update takes place. The following stored procedure uses the original value to check if another user has changed the data before it performs an update.

In order to execute this stored procedure, you define an @Original_pub_name SqlParameter object that uses the Original value of the field as its SourceVersion.

Note: Concurrency issues in disconnected data scenarios are an important topic. You should read more about this issue.

Once you’ve defined a SqlParameter object for each parameter identified in the stored procedure, you can add the SqlParameter objects to the Parameters collection of the SqlCommand object responsible for executing the stored procedure. The following code demonstrates adding a SqlParameter object to the Parameters collection.

   cmdUpdPubInfo.Parameters.Add(UpdParam)

As an alternative, the overloaded Add method allows you to create the SqlParameter object and add it to the collection in one step.

The Fill method of the DataAdapter will implicitly open the connection if it is closed and close it after the data is retrieved. If you explicitly open the connection, however, the DataAdapter will not close it.

In order to demonstrate how to use a SqlDataAdapter object in conjunction with a stored procedure to update data, open the Windows Application project you created earlier. Using the Server Explorer window, create the up_UpdPubName stored procedure in the Pubs database. Open the Publishers class in the Code Editor and add the following class-level declaration to create a SqlCommand object.

   Private cmdUpdPubInfo As SqlCommand

In the body of the class constructor, add code to instantiate the update command and set the Connection, CommandType, and CommandText properties.

   'Update command   cmdUpdPubInfo = New SqlCommand()   cmdUpdPubInfo.Connection = cnPubs   cmdUpdPubInfo.CommandType = _     CommandType.StoredProcedure   cmdUpdPubInfo.CommandText = _     "up_UpdPubName"

Next, define and add the necessary update parameters to the Parameters collection.

   'Update command parameters

Add code after the DataAdapter instantiation to set the UpdateCommand property of the DataAdapter to the cmdUpdPubInfo object.

   daPubs.UpdateCommand = cmdUpdPubInfo

Create a subprocedure called UpdatePubInfo that takes a DataSet object as an input parameter. In the body of the function, call the Update method of the DataAdapter object and pass in the DataSet.

Add a button to Form1 and add code to the button’s Update event that calls the UpdatePubInfo method of objPublisher. First, check if the DataSet has changes by calling the HasChanges method. If there are changes, filter the dsPublisher and pass only the changed rows by calling the GetChanges method of the DataSet.

Run the application in Debug mode. Make changes to the pub_name and click the Update button. Stop the application. Right-click on the publisher table node in the Server Explorer window and choose Retrieve Data from Table. Verify that the changes updated the database.

Now that you are familiar with using a stored procedure to implement updating data through the SqlDataApapter, you can implement data inserts and deletes in a similar manner. This will be an exercise left for the reader. The solution code for this article contains sample code that demonstrates inserts and updates using the SqlDataAdapter.

This article demonstrated how to use the SqlDataAdapter class and its parameters to update a database. You also read how to use the SqlDataAdapter in conjunction with stored procedures to propagate data changes in a disconnected DataSet back to the database. Encapsulating data update logic in stored procedures is an excellent way to improve the manageability, scalability, and security of your database-driven applications. One area this article does not address is data concurrency. Dealing with data concurrency is vital in a disconnected scenario.

   CREATE PROCEDURE dbo.up_GetPublisherInfo   AS   SELECT     pub_id, pub_name, city, state, country   FROM         publishers   RETURN   CREATE PROCEDURE dbo.up_UpdatePubInfo      (         @pub_id char (4),         @pub_name varchar (40),         @city varchar (20),         @state char (2),         @country varchar (30)      )   AS   UPDATE    publishers   SET              pub_name = @pub_name, city = @city, _   state = @state, country = @country   WHERE     (pub_id = @pub_id)   RETURN    oParam.Direction = ParameterDirection.Output   CREATE PROCEDURE dbo.up_updPubName   (      @pub_id char(4),      @pub_name varchar(40),      @Original_pub_name varchar(40)   )   AS   if exists(select pub_id from publishers            where (pub_id = @pub_id) AND            (pub_name = @Original_pub_name))   Begin   UPDATE publishers SET pub_name = @pub_name    WHERE (pub_id = @pub_id)   End    Dim UpdPubParam As New SqlParameter("@Original_pub_name", _   SqlDbType.VarChar, 40)   UpdAuthParam.SourceColumn = "pub_name"   UpdAuthParam.SourceVersion = DataRowVersion.Original   cmdUpdPubInfo.Parameters.Add( _      "@pub_id", SqlDbType.Char,4,"pub_id")   cmdUpdPubInfo.Parameters.Add( _     "@pub_id", SqlDbType.Char, 4, "pub_id")   cmdUpdPubInfo.Parameters.Add("@pub_name",      SqlDbType.VarChar, 40, "pub_name")   Dim UpdPubParam As New SqlParameter( _     "@Original_pub_name", _     SqlDbType.VarChar, 40, "pub_name")   UpdPubParam.SourceVersion = DataRowVersion.Original   cmdUpdPubInfo.Parameters.Add(UpdPubParam)   Public Sub UpdatePubInfo(ByVal dsChanges As DataSet)           daPubs.Update(dsChanges)   End Sub   If dsPubInfo.HasChanges Then               objPublishers.UpdatePubInfo(dsPubInfo.GetChanges)               dsPubInfo.Clear()               dsPubInfo = objPublishers.GetPubInfo   End If
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