/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
Example23_3.cs illustrates the use of adding, modifying, and deleting
a row in a DataTable object and synchronizing those changes with the
database
*/
using System;
using System.Data;
using System.Data.SqlClient;
public class Example23_3
{
public static void DisplayDataTable(DataTable myDataTable)
{
// display the columns for each row in the DataTable,
// using a DataRow object to access each row in the DataTable
foreach (DataRow myDataRow in myDataTable.Rows)
{
Console.WriteLine("CustomerID = " + myDataRow["CustomerID"]);
Console.WriteLine("CompanyName = " + myDataRow["CompanyName"]);
Console.WriteLine("ContactName = " + myDataRow["ContactName"]);
Console.WriteLine("Address = " + myDataRow["Address"]);
}
}
public static void AddRow(
DataTable myDataTable
)
{
Console.WriteLine("\nAdding a new row with CustomerID of 'T1COM'");
// step 1: use the NewRow() method of the DataRow object to create
// a new row in the DataTable
DataRow myNewDataRow = myDataTable.NewRow();
// step 2: set the values for the columns of the new row
myNewDataRow["CustomerID"] = "T1COM";
myNewDataRow["CompanyName"] = "T1 Company";
myNewDataRow["ContactName"] = "Jason Price";
myNewDataRow["Address"] = "1 Main Street";
// step 3: use the Add() method through the Rows property to add
// the new DataRow to the DataTable
myDataTable.Rows.Add(myNewDataRow);
// step 4: use the AcceptChanges() method of the DataTable to commit
// the changes
myDataTable.AcceptChanges();
}
public static void ModifyRow(
DataTable myDataTable
)
{
Console.WriteLine("\nModifying the new row");
// step 1: set the PrimaryKey property for the DataTable object
DataColumn[] myPrimaryKey = new DataColumn[1];
myPrimaryKey[0] = myDataTable.Columns["CustomerID"];
myDataTable.PrimaryKey = myPrimaryKey;
// step 2: use the Find() method to locate the DataRow
// in the DataTable using the primary key value
DataRow myEditDataRow = myDataTable.Rows.Find("T1COM");
// step 3: change the column values
myEditDataRow["CompanyName"] = "Widgets Inc.";
myEditDataRow["ContactName"] = "John Smith";
myEditDataRow["Address"] = "1 Any Street";
// step 4: use the AcceptChanges() method of the DataTable to commit
// the changes
myDataTable.AcceptChanges();
Console.WriteLine("myEditDataRow.RowState = " + myEditDataRow.RowState);
}
public static void RemoveRow(
DataTable myDataTable
)
{
Console.WriteLine("\nRemoving the new row");
// step 1: set the PrimaryKey property for the DataTable object
DataColumn[] myPrimaryKey = new DataColumn[1];
myPrimaryKey[0] = myDataTable.Columns["CustomerID"];
myDataTable.PrimaryKey = myPrimaryKey;
// step 2: use the Find() method to locate the DataRow
DataRow myRemoveDataRow = myDataTable.Rows.Find("T1COM");
// step 3: use the Delete() method to remove the DataRow
myRemoveDataRow.Delete();
// step 4: use the AcceptChanges() method of the DataTable to commit
// the changes
myDataTable.AcceptChanges();
}
public static void Main()
{
// formulate a string containing the details of the
// database connection
string connectionString =
"server=localhost;database=Northwind;uid=sa;pwd=sa";
// create a SqlConnection object to connect to the
// database, passing the connection string to the constructor
SqlConnection mySqlConnection =
new SqlConnection(connectionString);
// formulate a SELECT statement to retrieve the
// CustomerID, CompanyName, ContactName, and Address
// columns for the first row from the Customers table
string selectString =
"SELECT CustomerID, CompanyName, ContactName, Address " +
"FROM Customers " +
"WHERE CustomerID = 'ALFKI'";
// create a SqlCommand object to hold the SELECT statement
SqlCommand mySqlCommand = mySqlConnection.CreateCommand();
// set the CommandText property of the SqlCommand object to
// the SELECT string
mySqlCommand.CommandText = selectString;
// create a SqlDataAdapter object
SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter();
// set the SelectCommand property of the SqlAdapter object
// to the SqlCommand object
mySqlDataAdapter.SelectCommand = mySqlCommand;
// create a DataSet object to store the results of
// the SELECT statement
DataSet myDataSet = new DataSet();
// open the database connection using the
// Open() method of the SqlConnection object
mySqlConnection.Open();
// use the Fill() method of the SqlDataAdapter object to
// retrieve the rows from the table, storing the rows locally
// in a DataTable of the DataSet object
Console.WriteLine("Retrieving a row from the Customers table");
mySqlDataAdapter.Fill(myDataSet, "Customers");
// get the DataTable object from the DataSet object
DataTable myDataTable = myDataSet.Tables["Customers"];
// display the rows in the DataTable object
DisplayDataTable(myDataTable);
// add a new row
AddRow(myDataTable);
DisplayDataTable(myDataTable);
// modify a row
ModifyRow(myDataTable);
DisplayDataTable(myDataTable);
// remove a row
RemoveRow(myDataTable);
DisplayDataTable(myDataTable);
// use the Fill() method of the SqlDataAdapter object
// to synchronize the changes with the database
mySqlDataAdapter.Fill(myDataSet, "Customers");
// close the database connection using the Close() method
// of the SqlConnection object
mySqlConnection.Close();
}
}
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