key-constraints.aspx
来自「Professional ASP.NET source code」· ASPX 代码 · 共 171 行
ASPX
171 行
<%@Page Language="C#" debug="true"%>
<%@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>Adding Primary Keys and Foreign Keys to a Table</title>
<!-- #include file="..\global\style.inc" -->
</head>
<body bgcolor="#ffffff">
<span class="heading">Adding Primary Keys and Foreign Keys to a Table</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>Books SELECT command: <b><span id="outSelectBooks" runat="server"></span></b></div>
<div>Authors SELECT command: <b><span id="outSelectAuthors" runat="server"></span></b></div>
<div id="outError" runat="server"> </div>
<b>DataSet.Tables Collection</b>
<asp:datagrid id="dgrTables" runat="server" /><br />
<b>DataSet.Tables["Books"].Constraints Collection</b>
<asp:datagrid id="dgrBookCons" runat="server" /><br />
<b>DataSet.Tables["Authors"].Constraints Collection</b>
<asp:datagrid id="dgrAuthorCons" runat="server" /><br />
<b>Contents of DataSet.Tables["Books"]</b>
<asp:datagrid id="dgrBooksData" runat="server" /><br />
<b>Contents of DataSet.Tables["Authors"]</b>
<asp:datagrid id="dgrAuthorsData" runat="server" /><br />
<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 SELECT statement to extract the BookList data
string strSelectBooks = "SELECT * FROM BookList WHERE ISBN LIKE '18610033%'";
outSelectBooks.InnerText = strSelectBooks; // and display it
// specify the SELECT statement to extract the BookAuthor data
string strSelectAuthors = "SELECT * FROM BookAuthors WHERE ISBN LIKE '18610033%'";
outSelectAuthors.InnerText = strSelectAuthors; // and display it
// declare a variable to hold a DataSet object
DataSet objDataSet = new DataSet();
try
{
// create a new Connection object using the connection string
OleDbConnection objConnect = new OleDbConnection(strConnect);
// create a new Command object
OleDbCommand objCommand = new OleDbCommand();
// set the properties
objCommand.Connection = objConnect;
objCommand.CommandType = CommandType.Text;
objCommand.CommandText = strSelectBooks;
// create a new DataAdapter object
OleDbDataAdapter objDataAdapter = new OleDbDataAdapter();
// and assign the Command object to it
objDataAdapter.SelectCommand = objCommand;
// get the data from the "BookList" table in the database and
// put it into a table named "Books" in the DataSet object
objDataAdapter.Fill(objDataSet, "Books");
// change the SELECT statement in the Command object
objCommand.CommandText = strSelectAuthors;
// then get data from "BookAuthors" table into the DataSet
objDataAdapter.Fill(objDataSet, "Authors");
}
catch (Exception objError)
{
// display error details
outError.InnerHtml = "<b>* Error while accesing data</b>.<br />"
+ objError.Message + "<br />" + objError.Source;
return; // and stop execution
}
// now that the DataSet is filled, we can modify the tables it contains
// declare variables to refer to the DataTable and a DataColumn objects
DataTable objParentTable = objDataSet.Tables["Books"];
DataTable objChildTable = objDataSet.Tables["Authors"];
DataColumn objParentColumn = objParentTable.Columns["ISBN"];
DataColumn objChildColumn = objChildTable.Columns["ISBN"];
// create a new UniqueConstraint object and add to Constraints collection
UniqueConstraint objUnique = new UniqueConstraint("Unique_ISBN", objParentColumn);
objParentTable.Constraints.Add(objUnique);
// prevent the column from accepting Null values
objParentColumn.AllowDBNull = false;
// create an array of columns containing this column only
DataColumn[] objColumnArray = new DataColumn[1];
objColumnArray[0] = objParentColumn;
// and set this array as the columns for the Primary Key of the table
objParentTable.PrimaryKey = objColumnArray;
// now we can process the child table named "Authors"
// create an array of columns containing the ISBN and Lastname columns
objColumnArray = new DataColumn[2];
objColumnArray[0] = objChildColumn; // the ISBN column
objColumnArray[1] = objChildTable.Columns["Lastname"];
// prevent either of these columns containing Null
objColumnArray[0].AllowDBNull = false;
objColumnArray[1].AllowDBNull = false;
// set this column array as the primary key
objChildTable.PrimaryKey = objColumnArray;
// create a new ForeignKeyConstraint object
ForeignKeyConstraint objFKey = new ForeignKeyConstraint("FK_BookAuthors", objParentColumn, objChildColumn);
// set the "update" properties
objFKey.DeleteRule = Rule.Cascade;
objFKey.UpdateRule = Rule.Cascade;
// and add it to the Constraints collection
objChildTable.Constraints.Add(objFKey);
// --------------------------------------------------------------
// now we're ready to display the contents of the DataSet object
// bind the collection of Tables to the first DataGrid on the page
dgrTables.DataSource = objDataSet.Tables;
dgrTables.DataBind();
// bind the collection of Constraints to the second DataGrid on the page
dgrBookCons.DataSource = objDataSet.Tables["Books"].Constraints;
dgrBookCons.DataBind();
// bind the collection of Constraints to the third DataGrid on the page
dgrAuthorCons.DataSource = objDataSet.Tables["Authors"].Constraints;
dgrAuthorCons.DataBind();
// create a DataView object to use with the tables in the DataSet
DataView objDataView = new DataView();
// get the default view of the Books table into the DataView object
objDataView = objDataSet.Tables["Books"].DefaultView;
// and bind it to the next DataGrid on the page
dgrBooksData.DataSource = objDataView;
dgrBooksData.DataBind();
// then do the same for the Authors table
objDataView = objDataSet.Tables["Authors"].DefaultView;
dgrAuthorsData.DataSource = objDataView;
dgrAuthorsData.DataBind();
}
</script>
<!--------------------------------------------------------------------------->
<!-- #include file="..\global\foot.inc" -->
</body>
</html>
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