ControlParameter Class
Assembly: System.Web (in system.web.dll)
You can use the ControlParameter class to bind the value of a Control property, such as SelectedValue or SelectedIndex, to a parameter used in a parameterized SQL query, business object method, or filtering expression.
The ControlParameter class provides two properties in addition to those inherited from the Parameter class: ControlID and PropertyName. The ControlID property identifies which Control instance to bind to and the PropertyName property identifies the public property of the Control from which the ControlParameter class retrieves a value.
The following code example demonstrates how to use a ControlParameter object to bind data displayed in a ListBox control to the selected value of a DropDownList control in a declarative scenario. The ControlParameter object is added to the SelectParameters collection of the SqlDataSource control on the form, and corresponds to the "@Title" placeholder text in the SelectCommand property.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>ASP.NET Example</title>
</head>
<body>
<form id="form1" runat="server">
<p><asp:DropDownList
id="DropDownList1"
runat="server"
AutoPostBack="True">
<asp:ListItem Selected="True">Sales Representative</asp:ListItem>
<asp:ListItem>Sales Manager</asp:ListItem>
<asp:ListItem>Vice President, Sales</asp:ListItem>
</asp:DropDownList></p>
<asp:SqlDataSource
id="SqlDataSource1"
runat="server"
ConnectionString="Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;"
SelectCommand="SELECT LastName FROM Employees WHERE Title = @Title">
<SelectParameters>
<asp:ControlParameter Name="Title" ControlId="DropDownList1" PropertyName="SelectedValue"/>
</SelectParameters>
</asp:SqlDataSource>
<p><asp:ListBox
id="ListBox1"
runat="server"
DataSourceID="SqlDataSource1"
DataTextField="LastName">
</asp:ListBox></p>
</form>
</body>
</html>
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