update-with-transaction.aspx
来自「Professional ASP.NET source code」· ASPX 代码 · 共 166 行
ASPX
166 行
<%@Page Language="C#"%>
<%@Import Namespace="System.Data" %>
<%@Import Namespace="System.Data.OleDb" %>
<%@ Register TagPrefix="wrox" TagName="connect" Src="..\global\connect-strings.ascx" %>
<!DOCTYPE HTML PUBLIC "-// W3C// DTD HTML 4.0 Transitional// EN">
<html><head>
<title>Transactional Data Updates with a Command Object</title>
<!-- #include file="..\global\style.inc" -->
</head>
<body bgcolor="#ffffff">
<span class="heading">Transactional Data Updates with a Command Object</span><hr />
<!--------------------------------------------------------------------------->
<%// -- insert connection string script --%>
<wrox:connect id="ctlConnectStrings" runat="server"/>
<div>Connection string: <b><span id="outConnect" runat="server"></span></b></div>
<div>SQL statement 1: <b><span id="outSQL1" runat="server"></span></b></div>
<div>SQL statement 2: <b><span id="outSQL2" runat="server"></span></b></div>
<div>SQL statement 3: <b><span id="outSQL3" runat="server"></span></b></div>
<div id="outError" runat="server"> </div>
<div id="outResult" runat="server"></div>
<script language="C#" runat="server">
void Page_Load(Object sender, EventArgs e)
{
// get connection string from ..\global\connect-strings.ascx user control
string strConnect = ctlConnectStrings.OLEDBConnectionString;
outConnect.InnerText = strConnect; // and display it
// specify the SQL statements to update the data
string strNow, strSQL1, strSQL2, strSQL3;
DateTime datNow = DateTime.Now;
strNow = datNow.ToString("dd-M-yy \a\t hh:mm:ss");
strSQL1 = "UPDATE BookList SET Title = 'Book One Written on "
+ strNow + "' WHERE ISBN='1861000375'";
outSQL1.InnerText = strSQL1; // and display it
strSQL2 = "UPDATE BookList SET Title = 'Book Two Written on "
+ strNow + "' WHERE ISBN='1861000383'";
outSQL2.InnerText = strSQL2; // and display it
strSQL3 = "UPDATE BookList SET Title = 'Book Three Written on "
+ strNow + "' WHERE ISBN='1861000391'";
outSQL3.InnerText = strSQL3; // and display it
// create a new Connection object using the connection string
OleDbConnection objConnect = new OleDbConnection(strConnect);
// create a new Command object to use to access the data
OleDbCommand objCommand = new OleDbCommand();
// declare an Integer variable to hold the number of records affected
int intRowsAffected = 0;
// declare a variable to hold a Transaction object
OleDbTransaction objTransaction = null;
try
{
// open the connection to the database
objConnect.Open();
// start a transaction for this connection
objTransaction = objConnect.BeginTransaction();
// specify the Connection object and command type for the Command
objCommand.Connection = objConnect;
objCommand.CommandType = CommandType.Text;
// attach the current transaction to the Command object
// must be done after setting Connection property
objCommand.Transaction = objTransaction;
// specify the select statement to use for the first update
objCommand.CommandText = strSQL1;
// execute the SQL statement against the command to fill the DataReader
// keep track of number of records originally updated
intRowsAffected += objCommand.ExecuteNonQuery();
// repeat using the select statement to use for the second update
objCommand.CommandText = strSQL2;
intRowsAffected += objCommand.ExecuteNonQuery();
// repeat using the select statement to use for the third update
objCommand.CommandText = strSQL3;
intRowsAffected += objCommand.ExecuteNonQuery();
}
catch (Exception objError)
{
// error encountered so roll back all the updates
objTransaction.Rollback();
// display error details
outError.InnerHtml = "<b>* Error while updating original data</b>.<br />"
+ objError.Message + "<br />" + objError.Source;
return; // and stop execution
}
// all seems to be OK so can commit all the updates
// however, only do so if current time has 'odd' seconds
string strCommit;
if (datNow.Second % 2 == 0)
{
objTransaction.Rollback();
strCommit = "rolled back";
}
else
{
objTransaction.Commit();
strCommit = "committed";
}
// now read the data back again. Specify a SQL statement to
// extract just the changes records in the Command object
// release the transaction object so we can use the Command again
objCommand.Transaction = null;
objCommand.CommandText = "SELECT * FROM BookList WHERE ISBN LIKE '18610003%'";
// show the number of records affected
string strResult = "Executed SQL statement, <b>" + intRowsAffected.ToString()
+ "</b> record(s) affected<br />Transaction was <b>" + strCommit
+ "</b><br />Reading back from the database...</br>";
try
{
// declare a variable to hold a DataReader object
OleDbDataReader objDataReader;
// execute the SQL statement against the command to fill the DataReader
objDataReader = objCommand.ExecuteReader();
// iterate through the records in the DataReader getting field values
// the Read method returns False when there are no more records
while (objDataReader.Read())
strResult += "ISBN='<b>" + objDataReader["ISBN"] + "</b>' Title='<b>"
+ objDataReader["Title"] + "'</b><br />";
// close the DataReader and Connection
objDataReader.Close();
objConnect.Close();
}
catch (Exception objError)
{
// display error details
outError.InnerHtml = "<b>* Error while accessing updated data</b>.<br />"
+ objError.Message + "<br />" + objError.Source;
return; // and stop execution
}
// add closing table tag and display the results
outResult.InnerHtml = strResult;
}
</script>
<!--------------------------------------------------------------------------->
<!-- #include file="..\global\foot.inc" -->
</body>
</html>
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