Microsoft KB Archive/307587

From BetaArchive Wiki

Article ID: 307587

Article Last Modified on 3/29/2007


APPLIES TO

  • Microsoft Visual C# 2005
  • Microsoft Visual C# .NET 2003 Standard Edition
  • Microsoft Visual C# .NET 2002 Standard Edition


This article was previously published under Q307587

For a Microsoft Visual Basic .NET version of this article, see 301248.

For a Microsoft Visual C++ .NET version of this article, see 815660.


This article refers to the following Microsoft .NET Framework Class Library namespaces:

  • System.Data
  • System.Data.SqlClient

SUMMARY

This step-by-step article shows you how to take a DataSet that contains data (which is loaded from a database), how to modify that data, and then how to send it back to the database to update the original source.

DataSet objects, a key part of data access in the Microsoft .NET Framework, are in-memory objects that can hold tables, views, and relationships.

Requirements

The following list outlines the recommended hardware, software, network infrastructure, and service packs that you need:

  • Microsoft Windows Server 2003, Microsoft Windows 2000 Professional, Microsoft Windows 2000 Server, Microsoft Windows 2000 Advanced Server, or Microsoft Windows NT 4.0 Server
  • Microsoft SQL Server version 7.0, Microsoft SQL Server 2000, or Microsoft Data Engine (MSDE) with the PUBS sample database installed
  • Microsoft Visual Studio 2005 or Microsoft Visual Studio .NET

This article assumes that you are familiar with the following topics:

  • Database terminology
  • Structured Query Language (SQL)

How to update a database from a DataSet object

This section demonstrates how to use the DataSet object to update data in a database. It is important to remember that you can also use a SqlCommand object to insert, update, and delete data in a database directly.

To help you understand this article, click the article number below to view the article in the Microsoft Knowledge Base:

314145 How To Populate a DataSet Object from a Database by Using Visual C# .NET


Some of the topics that are covered in 314145 include how to retrieve data from a database and into a DataSet, and how the DataSet is separate and distinct from the database.

After the DataSet is loaded, you can modify the data. The DataSet will track these changes. The DataSet object can be considered an in-memory cache of data that is retrieved from a database. The DataSet object consists of a collection of tables, relationships, and constraints.

To update a DataSet and send those updates back to the database, follow these steps:

  1. Start Visual Studio 2005 or Visual Studio .NET.
  2. Create a new Console Application in Visual C#. Visual Studio creates a Static Class by default and an empty Main() procedure.

  3. Make sure that the project contains a reference to the System and System.Data namespaces. Use the using statement on the System, System.Data, and System.Data.SqlClient namespaces so that you are not required to qualify declarations from these namespaces later in your code. You must use these statements prior to any other declarations.

    using System;
using System.Data;
using System.Data.SqlClient;

  4. Before you can modify the data and submit the changes back to the database, you must load the information into the DataSet. For the detailed procedure, see 314145. To avoid duplication, the code in this step is not presented in detail.

    The connection string in the following code points to a SQL Server that is located on the local computer (or the computer where the code is running)To summarize, a connection is created, and then a data adapter is created, which is used to fill the DataSet with data.
    Note You must change User ID <username> and password to the correct values before you run this code. Make sure that User ID has the appropriate permissions to perform this operation on the database.

    string sConnectionString;

// Modify the following string to correctly connect to your SQL Server.
sConnectionString = "Password=<strong password>;User ID=<username>;"
    + "Initial Catalog=pubs;"
    + "Data Source=(local)";

SqlConnection objConn
    = new SqlConnection(sConnectionString);
objConn.Open();

// Create an instance of a DataAdapter.
SqlDataAdapter daAuthors 
    = new SqlDataAdapter("Select * From Authors", objConn);

// Create an instance of a DataSet, and retrieve data from the Authors table.
DataSet dsPubs = new DataSet("Pubs");
daAuthors.FillSchema(dsPubs,SchemaType.Source, "Authors");
daAuthors.Fill(dsPubs,"Authors");

  5. Now that the data is loaded, you can modify it. There are many ways to add a row (or record). This code sample uses a three step procedure:

    • Obtain a new DataRow object from the DataTable.
    • Set the DataRow field values as necessary.
    • Pass that new object into the Add method of the DataTable.Rows collection.

    Paste the following code after the code in step 4:

    //****************
// BEGIN ADD CODE 
// Create a new instance of a DataTable.
DataTable tblAuthors;
tblAuthors = dsPubs.Tables["Authors"];

DataRow drCurrent;
// Obtain a new DataRow object from the DataTable.
drCurrent = tblAuthors.NewRow();

// Set the DataRow field values as necessary.
drCurrent["au_id"] = "993-21-3427";
drCurrent["au_fname"] = "George";
drCurrent["au_lname"] = "Johnson";
drCurrent["phone"] = "800 226-0752";
drCurrent["address"] = "1956 Arlington Pl.";
drCurrent["city"] = "Winnipeg";
drCurrent["state"] = "MB";
drCurrent["contract"] = 1;

// Pass that new object into the Add method of the DataTable.
tblAuthors.Rows.Add(drCurrent);
Console.WriteLine("Add was successful, Click any key to continue!!");
Console.ReadLine();

// END ADD CODE

  6. To edit existing rows, obtain the appropriate DataRow object, and then provide new values for one or more columns. You must first find the correct row, which is much easier because you loaded the schema of the table as well as the data (the call to FillSchema in step 4). With the schema in place, the table knows which column is its primary key, and the Find method of the Rows collection is available.

    The Find method returns the DataRow object with a specific value in its primary key (in this case, au_id). After you have that DataRow, you can modify the columns. You do not have to wrap the modifications in BeginEdit and EndEdit, but this simplifies the work that the DataSet has to do and allows the DataSet to perform its validation checks simultaneously when EndEdit is called. Paste the following code after the ADD code:

    //*****************
// BEGIN EDIT CODE 

drCurrent = tblAuthors.Rows.Find("213-46-8915");
drCurrent.BeginEdit();
drCurrent["phone"] = "342" + drCurrent["phone"].ToString().Substring(3);
drCurrent.EndEdit();
Console.WriteLine("Record edited successfully, Click any key to continue!!");
Console.ReadLine();

// END EDIT CODE

  7. To update the original database with all of these changes, pass the DataSet into the Update method of the DataAdapter object.

    However, before you can call Update, you must set the InsertCommand, UpdateCommand, and DeleteCommand properties of the DataAdapter object. You can manually write SQL and populate these three properties with corresponding SqlCommand objects, but you can also use Visual Studio .NET to generate these three commands automatically.

    To generate the required commands when they are needed, you must create an instance of the SqlCommandBuilder object and use the DataAdapter in the constructor. If you want to use this method, which is illustrated in the code sample to follow, you must have primary key information available for your table. To access primary key information, call FillSchema, and then set the MissingSchemaAction property of your DataAdapter to AddWithKey, or manually set the primary key in your code. Paste the following code after the EDIT code:

    //*****************
// BEGIN SEND CHANGES TO SQL SERVER 

SqlCommandBuilder objCommandBuilder = new SqlCommandBuilder(daAuthors);
daAuthors.Update(dsPubs, "Authors");
Console.WriteLine("SQL Server updated successfully, Check Server explorer to see changes");
Console.ReadLine();

// END SEND CHANGES TO SQL SERVER

  8. To delete a row completely, use the Delete method of the DataRow object. Note that the Rows collection contains two methods, Remove and RemoveAt, which seem to delete the row but instead just remove the row from the collection. Only the Delete method sends your deletion back to the source database. Paste the following code after the SEND CHANGES TO SQL SERVER code:

    //*****************
//BEGIN DELETE CODE 

drCurrent = tblAuthors.Rows.Find("993-21-3427");
drCurrent.Delete();
Console.WriteLine("Record deleted successfully, Click any key to continue!!"); 
Console.ReadLine();

//END DELETE CODE

  9. Send the changes to SQL Server to remove the record that you added earlier. Paste the following code after the DELETE code:

    //*****************
// CLEAN UP SQL SERVER
daAuthors.Update(dsPubs, "Authors");
Console.WriteLine("SQL Server updated successfully, Check Server explorer to see changes");
Console.ReadLine();
  10. Save your project.
  11. On the Debug menu, click Start to run the project. Notice that several message boxes appear, which indicate the progress of the code and allow you to review the current state of the data as the code progresses.

Complete code listing

using System;
using System.Data;
using System.Data.SqlClient;

namespace PopulateDataSet
{

    /// <summary>
    /// Summary description for Class1.
    /// </summary>
    class Class1
    {
        static void Main(string[] args)
        {
            string sConnectionString;

            // Modify the following string to correctly connect to your SQL Server.
            sConnectionString = "Password=;User ID=sa;"
                + "Initial Catalog=pubs;"
                + "Data Source=(local)";

            SqlConnection objConn
                = new SqlConnection(sConnectionString);
            objConn.Open();

            // Create an instance of a DataAdapter.
            SqlDataAdapter daAuthors 
                = new SqlDataAdapter("Select * From Authors", objConn);

            // Create an instance of a DataSet, and retrieve 
            // data from the Authors table.
            DataSet dsPubs = new DataSet("Pubs");
            daAuthors.FillSchema(dsPubs,SchemaType.Source, "Authors");
            daAuthors.Fill(dsPubs,"Authors"); 
            //****************
            // BEGIN ADD CODE 
            // Create a new instance of a DataTable.
            DataTable tblAuthors;
            tblAuthors = dsPubs.Tables["Authors"];

            DataRow drCurrent;
            // Obtain a new DataRow object from the DataTable.
            drCurrent = tblAuthors.NewRow();

            // Set the DataRow field values as necessary.
            drCurrent["au_id"] = "993-21-3427";
            drCurrent["au_fname"] = "George";
            drCurrent["au_lname"] = "Johnson";
            drCurrent["phone"] = "800 226-0752";
            drCurrent["address"] = "1956 Arlington Pl.";
            drCurrent["city"] = "Winnipeg";
            drCurrent["state"] = "MB";
            drCurrent["contract"] = 1;

            // Pass that new object into the Add method of the DataTable.
            tblAuthors.Rows.Add(drCurrent);
            Console.WriteLine("Add was successful, Click any key to continue!!");
            Console.ReadLine();

            // END ADD CODE   
            //*****************
            // BEGIN EDIT CODE 

            drCurrent = tblAuthors.Rows.Find("213-46-8915");
            drCurrent.BeginEdit();
            drCurrent["phone"] = "342" + drCurrent["phone"].ToString().Substring(3);
            drCurrent.EndEdit();
            Console.WriteLine("Record edited successfully, Click any key to continue!!");
            Console.ReadLine();
            
            // END EDIT CODE   
            //*****************
            // BEGIN SEND CHANGES TO SQL SERVER 

            SqlCommandBuilder objCommandBuilder = new SqlCommandBuilder(daAuthors);
            daAuthors.Update(dsPubs, "Authors");
            Console.WriteLine("SQL Server updated successfully, Check Server explorer to see changes");
            Console.ReadLine();
            
            // END SEND CHANGES TO SQL SERVER 
            //*****************
            //BEGIN DELETE CODE 

            drCurrent = tblAuthors.Rows.Find("993-21-3427");
            drCurrent.Delete();
            Console.WriteLine("SRecord deleted successfully, Click any key to continue!!"); 
            Console.ReadLine();
       
            //END DELETE CODE  
            //*****************
            // CLEAN UP SQL SERVER
            daAuthors.Update(dsPubs, "Authors");
            Console.WriteLine("SQL Server updated successfully, Check Server explorer to see changes");
            Console.ReadLine();             
            
        }
    }
}

REFERENCES

For more information about using ADO.NET, DataSet objects, and SQL, visit the following Microsoft Web sites:

Diving into Data Access (an MSDN Voices column)
http://msdn2.microsoft.com/en-us/library/ms810288.aspx


ADO.NET for the ADO Programmer
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ dndotnet/html/adonetprogmsdn.asp


MSDN Online .NET Developer Center
http://msdn2.microsoft.com/en-us/netframework/default.aspx


Keywords: kbhowtomaster kbsqlclient kbsystemdata KB307587



Send feedback to Microsoft

© Microsoft Corporation. All rights reserved.


Retrieved from ‘https://www.betaarchive.com/wiki/index.php?title=Microsoft_KB_Archive/307587&oldid=330275’
the Creative Commons 3.0 ShareAlike (except the Microsoft KB Archive).
Powered by MediaWiki