QueryStringParameter Class
Binds the value of an HTTP request query-string field to a parameter object.
Assembly: System.Web (in System.Web.dll)
You can use the QueryStringParameter class to bind the value of a field that is passed as part of an HTTP request query string to a parameter that is used in a parameterized query or command. The field is retrieved from the QueryString collection.
Controls that bind data to the parameter might throw an exception if a QueryStringParameter object is referenced, but no corresponding query-string name/value pair is passed. Similarly, they might display no data if the query-string field name is passed without a corresponding value. To avoid these situations, set the DefaultValue property where appropriate.
The QueryStringParameter class provides the QueryStringField property, which identifies the name of the query string value to bind to. It also provides the properties that are inherited from the Parameter class.
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The QueryStringParameter class does not validate the value that is passed; it provides the raw value. However, you can validate the value of a QueryStringParameter object in a data source control. To do so, handle the Selecting, Updating, Inserting, or Deleting event of the data source control and check the parameter value in the event handler. If the value of the parameter does not pass the validation tests, you can cancel the data operation by setting the Cancel property of the associated CancelEventArgs class to true. |
The following example shows how to create a QueryStringParameter object to use as a filter when you display data in a GridView control. You add the QueryStringParameter object to the AccessDataSource control's FilterParameters collection. The parameter object binds the value of the query-string field named country to its FilterExpression string. Because no DefaultValue property is specified for the parameter, if no field named country is passed with the query string, the AccessDataSource control throws a NullReferenceException exception. If a field named country is passed but has no value, the GridView control displays no data.
The following example shows how to create a QueryStringParameter object to display data from an Access database by using a parameterized SQL query. The AccessDataSource object retrieves records that are then displayed in a GridView control. The GridView control is also editable, and lets users update the status of orders in the Northwind Traders Orders table.
- AspNetHostingPermission
for operating in a hosted environment. Demand value: LinkDemand; Permission value: Minimal.
- AspNetHostingPermission
for operating in a hosted environment. Demand value: InheritanceDemand; Permission value: Minimal.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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