QueryExtender Class

Definition

Namespace:

System.Web.UI.WebControls

Assembly:

System.Web.Extensions.dll

Enables data from a data source to be filtered without an explicit Where clause in the data source.

public ref class QueryExtender : System::Web::UI::Control

[System.Drawing.ToolboxBitmap(typeof(System.Web.UI.WebControls.QueryExtender), "QueryExtender.bmp")]
public class QueryExtender : System.Web.UI.Control

[<System.Drawing.ToolboxBitmap(typeof(System.Web.UI.WebControls.QueryExtender), "QueryExtender.bmp")>]
type QueryExtender = class
    inherit Control

Public Class QueryExtender
Inherits Control

Inheritance

Object

Control

QueryExtender

Attributes

ToolboxBitmapAttribute

Examples

The following example shows how to use the QueryExtender control to provide a search function in a Web page. The QueryExtender control uses the text that is entered in the TextBoxSearch control to search for contents in the ProductName and Supplier.CompanyName columns of a Products table in the data that is returned from the LinqDataSource control. The SearchExpression object is used to perform the search. The DataFields property specifies the data fields to search. The SearchType property specifies the type of search to perform. The ControlParameter element specifies the control that contains the text to use for the search. This code example is part of a larger example that is provided in Walkthrough: Filtering Data in a Web Page Using Declarative Syntax.

<asp:LinqDataSource ID="dataSource" runat="server"   
    TableName="Products">  
</asp:LinqDataSource>  
<asp:QueryExtender TargetControlID="dataSource" runat="server">  
  <asp:SearchExpression DataFields="ProductName, Supplier.CompanyName"   
        SearchType="StartsWith">  
    <asp:ControlParameter ControlID="TextBoxSearch" />  
  </asp:SearchExpression>  
</asp:QueryExtender>  

The following example shows how to use the QueryExtender control to search a Web page for values in a specified range. The QueryExtender control uses the values that are entered in the TextBoxFrom and TextBoxTo controls to search for values in the ProductName and Supplier.CompanyName columns of a Products table in the data that is returned from the LinqDataSource control. The ControlParameter element specifies the text box controls that contain the minimum and maximum values to use for searching the range. The MinType and MaxType properties specify that the minimum and maximum values must be included in the data that is returned. This code example is part of a larger example provided in Walkthrough: Filtering Data in a Web Page Using Declarative Syntax.

<asp:LinqDataSource ID="dataSource" runat="server"   
    TableName="Products">  
</asp:LinqDataSource>  
<asp:QueryExtender TargetControlID="dataSource" runat="server">  
  <asp:RangeExpression DataField="UnitPrice" MinType="Inclusive"   
        MaxType="Inclusive">  
    <asp:ControlParameter ControlID="TextBoxFrom" />  
    <asp:ControlParameter ControlID="TexBoxTo" />  
  </asp:RangeExpression>  
</asp:QueryExtender>  

Remarks

In this topic:

• Introduction

• Background

• Filter Options

• Tasks

• Declarative Syntax

Introduction

The QueryExtender control is used to create filters for data that is retrieved from a data source, without using an explicit Where clause in the data source. The QueryExtender control can be used to specify filtering by using declarative syntax.

Background

Filtering excludes data from a data source by displaying only the records that meet specified criteria. Filtering enables you to present different views of the data that is in a data set without affecting the data in the data set.

Filtering typically requires that you create a Where clause to apply to the command that queries the data source. However, the Where property of the data source control might not expose the full functionality that is available. For example, the QueryExtender control enables you to query a table by searching for strings at the beginning, end or anywhere in .data field.

To expose the full functionality that is available in LINQ and to make filtering data easier, ASP.NET provides the QueryExtender control. The QueryExtender control has the following benefits:

• It provides a richer filtering experience than writing a Where clause. For example, you can search a Products table for Boolean values by using the PropertyExpression filter without writing a query.

• It lets you specify filters by using the same syntax for the LinqDataSource and EntityDataSource controls and for any other data source controls that you might use.

• It can be used with LinqDataSource control, with a EntityDataSource control, or with third-party data sources.

Filter Options

The QueryExtender control supports a variety of options that you can use to filter data. The control lets you search strings, search numeric values in a specified range, and compare a property value in a table to a specified value. The control also lets you sort the data and provide custom queries.

These options are provided as LINQ expressions in the QueryExtender control. The QueryExtender control also supports expressions that are specific to ASP.NET Dynamic Data applications.

The following table lists the options that you can use to filter data in the QueryExtender control.

Expression	Description
ControlFilterExpression	(Dynamic Data only) Builds a database query by using the data key that is selected in a source data-bound control. For information about how to use this filter option, see How to: Filter Table Rows Using Values from a Parent Table in Dynamic Data.
CustomExpression	Specifies a user-defined expression for a data source. The custom LINQ expression can be invoked in an event handler.
DynamicFilterExpression	(Dynamic Data only) Builds a database query by using the specified DynamicFilter control. For information about how to use this filter option, see How to: Filter Table Rows Using Foreign Key in Dynamic Data.
MethodExpression	Specifies a user-defined LINQ expression for a data source. The expression is invoked in a method.
OrderByExpression	Applies a sort expression to an IQueryable data source object. After you apply the OrderByExpression value, you can apply additional sort operations by specifying a ThenByExpressions value.
PropertyExpression	Compares the properties the data field and property values that are specified in the WhereParameters collection.
RangeExpression	Determines whether a value is greater than or less than a specified value, or whether a value is between two values.
SearchExpression	Compares values in a field or fields to a specified string value.

You can use these QueryExtender options individually or you can combine them to provide complex filtering in a Web page. For more information, see QueryExtender Web Server Control Overview. Walkthrough: Filtering Data in a Web Page Using Declarative Syntax

Tasks

The following table lists tasks that show how to use the QueryExtender control to filter data.

Document	Task
Walkthrough: Filtering Data in a Web Page Using Declarative Syntax	Shows how to use the filter options that the QueryExtender control provides.

Declarative Syntax

<asp:QueryExtender   
    EnableViewState="True|False"  
    ID="string"  
    OnDataBinding="DataBiding event handler"  
    OnDisposed="Disposed event handler"  
    OnInit="Init event handler  
    OnLoad="Load event handler"  
    OnPreRender="PreRender event handler"  
    OnUnload="UnLoad event handler"  
    Runat="server"  
    TargetControlID="string"  
    Visible="True|False"  
>  
        <asp:ControlFilterExpression   
            ControlD="string"  
            Column="string">   
        </asp:ControlFilterExpression>  
        <asp:DynamicFilterExpression  
            ControlD="string"  
        </asp:DynamicFilterExpression>  
        <asp:CustomExpression="string"  
            OnQuerying="OnQuerying event handler">  
        </asp:CustomExpression>  
        <asp:OrderByExpression="string"  
            DataField="string"  
            Direction="string">  
            <asp:ThenByExpression  
                 DataField="string"  
                 Direction="string"  
            </asp:ThenBy>  
        </asp:OrderByExpression>  
        <asp:PropertyExpression="string">  
                <!-- child controls -->  
        </asp:PropertyExpression  
        >  
        <asp:RangeExpression="integer"  
            Datafield="string"  
            MaxType="Exclusive|Inclusive|None"  
            MinType="Exclusive|Inclusive|None">  
                <!--child controls-->  
        </asp:RangeExpression>  
        <asp:SearchExpression="string"  
            ComparisonType="CurrentCulture|CurrentCultureIgnoreCase|  
                InvariantCulture|InvariantCultureIgnoreCase|  
                Ordinal|OrdinalIgnoreCase"  
            DataField="string"  
            SearchType="Contains|EndsWith|StartsWith">  
                <!--child controls-->  
        </asp:SearchExpression>  
</asp:QueryExtender>  

Constructors

QueryExtender()

Initializes a new instance of the QueryExtender Class.

Properties

Adapter	Gets the browser-specific adapter for the control. (Inherited from Control)
AppRelativeTemplateSourceDirectory	Gets or sets the application-relative virtual directory of the Page or UserControl object that contains this control. (Inherited from Control)
BindingContainer	Gets the control that contains this control's data binding. (Inherited from Control)
ChildControlsCreated	Gets a value that indicates whether the server control's child controls have been created. (Inherited from Control)
ClientID	Gets the control ID for HTML markup that is generated by ASP.NET. (Inherited from Control)
ClientIDMode	Gets or sets the algorithm that is used to generate the value of the ClientID property. (Inherited from Control)
ClientIDSeparator	Gets a character value representing the separator character used in the ClientID property. (Inherited from Control)
Context	Gets the HttpContext object associated with the server control for the current Web request. (Inherited from Control)
Controls	Gets a ControlCollection object that represents the child controls for a specified server control in the UI hierarchy. (Inherited from Control)
DataItemContainer	Gets a reference to the naming container if the naming container implements IDataItemContainer. (Inherited from Control)
DataKeysContainer	Gets a reference to the naming container if the naming container implements IDataKeysControl. (Inherited from Control)
DataSource	Gets the data source control (IDataSource object) to use for the query.
DesignMode	Gets a value indicating whether a control is being used on a design surface. (Inherited from Control)
EnableTheming	Gets or sets a value indicating whether themes apply to this control. (Inherited from Control)
EnableViewState	Gets or sets a value indicating whether the server control persists its view state, and the view state of any child controls it contains, to the requesting client. (Inherited from Control)
Events	Gets a list of event handler delegates for the control. This property is read-only. (Inherited from Control)
Expressions	Gets the collection of expressions that are applied to the IDataSource control.
HasChildViewState	Gets a value indicating whether the current server control's child controls have any saved view-state settings. (Inherited from Control)
ID	Gets or sets the programmatic identifier assigned to the server control. (Inherited from Control)
IdSeparator	Gets the character used to separate control identifiers. (Inherited from Control)
IsChildControlStateCleared	Gets a value indicating whether controls contained within this control have control state. (Inherited from Control)
IsTrackingViewState	Gets a value that indicates whether the server control is saving changes to its view state. (Inherited from Control)
IsViewStateEnabled	Gets a value indicating whether view state is enabled for this control. (Inherited from Control)
LoadViewStateByID	Gets a value indicating whether the control participates in loading its view state by ID instead of index. (Inherited from Control)
NamingContainer	Gets a reference to the server control's naming container, which creates a unique namespace for differentiating between server controls with the same ID property value. (Inherited from Control)
Page	Gets a reference to the Page instance that contains the server control. (Inherited from Control)
Parent	Gets a reference to the server control's parent control in the page control hierarchy. (Inherited from Control)
RenderingCompatibility	Gets a value that specifies the ASP.NET version that rendered HTML will be compatible with. (Inherited from Control)
Site	Gets information about the container that hosts the current control when rendered on a design surface. (Inherited from Control)
SkinID	Gets or sets the skin to apply to the control. (Inherited from Control)
TargetControlID	Gets or sets the ID of the IDataSource control to use for the query.
TemplateControl	Gets or sets a reference to the template that contains this control. (Inherited from Control)
TemplateSourceDirectory	Gets the virtual directory of the Page or UserControl that contains the current server control. (Inherited from Control)
UniqueID	Gets the unique, hierarchically qualified identifier for the server control. (Inherited from Control)
ValidateRequestMode	Gets or sets a value that indicates whether the control checks client input from the browser for potentially dangerous values. (Inherited from Control)
ViewState	Gets a dictionary of state information that allows you to save and restore the view state of a server control across multiple requests for the same page. (Inherited from Control)
ViewStateIgnoresCase	Gets a value that indicates whether the StateBag object is case-insensitive. (Inherited from Control)
ViewStateMode	Gets or sets the view-state mode of this control. (Inherited from Control)
Visible	Gets or sets a value that indicates whether a server control is rendered as UI on the page. (Inherited from Control)

Methods

AddedControl(Control, Int32)	Called after a child control is added to the Controls collection of the Control object. (Inherited from Control)
AddParsedSubObject(Object)	Notifies the server control that an element, either XML or HTML, was parsed, and adds the element to the server control's ControlCollection object. (Inherited from Control)
ApplyStyleSheetSkin(Page)	Applies the style properties defined in the page style sheet to the control. (Inherited from Control)
BeginRenderTracing(TextWriter, Object)	Begins design-time tracing of rendering data. (Inherited from Control)
BuildProfileTree(String, Boolean)	Gathers information about the server control and delivers it to the Trace property to be displayed when tracing is enabled for the page. (Inherited from Control)
ClearCachedClientID()	Sets the cached ClientID value to null. (Inherited from Control)
ClearChildControlState()	Deletes the control-state information for the server control's child controls. (Inherited from Control)
ClearChildState()	Deletes the view-state and control-state information for all the server control's child controls. (Inherited from Control)
ClearChildViewState()	Deletes the view-state information for all the server control's child controls. (Inherited from Control)
ClearEffectiveClientIDMode()	Sets the ClientIDMode property of the current control instance and of any child controls to Inherit. (Inherited from Control)
CreateChildControls()	Called by the ASP.NET page framework to notify server controls that use composition-based implementation to create any child controls they contain in preparation for posting back or rendering. (Inherited from Control)
CreateControlCollection()	Creates a new ControlCollection object to hold the child controls (both literal and server) of the server control. (Inherited from Control)
DataBind()	Binds a data source to the invoked server control and all its child controls. (Inherited from Control)
DataBind(Boolean)	Binds a data source to the invoked server control and all its child controls with an option to raise the DataBinding event. (Inherited from Control)
DataBindChildren()	Binds a data source to the server control's child controls. (Inherited from Control)
Dispose()	Enables a server control to perform final clean up before it is released from memory. (Inherited from Control)
EndRenderTracing(TextWriter, Object)	Ends design-time tracing of rendering data. (Inherited from Control)
EnsureChildControls()	Determines whether the server control contains child controls. If it does not, it creates child controls. (Inherited from Control)
EnsureID()	Creates an identifier for controls that do not have an identifier assigned. (Inherited from Control)
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
FindControl(String, Int32)	Searches the current naming container for a server control with the specified id and an integer, specified in the pathOffset parameter, which aids in the search. You should not override this version of the FindControl method. (Inherited from Control)
FindControl(String)	Searches the current naming container for a server control with the specified id parameter. (Inherited from Control)
Focus()	Sets input focus to a control. (Inherited from Control)
GetDesignModeState()	Gets design-time data for a control. (Inherited from Control)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetRouteUrl(Object)	Gets the URL that corresponds to a set of route parameters. (Inherited from Control)
GetRouteUrl(RouteValueDictionary)	Gets the URL that corresponds to a set of route parameters. (Inherited from Control)
GetRouteUrl(String, Object)	Gets the URL that corresponds to a set of route parameters and a route name. (Inherited from Control)
GetRouteUrl(String, RouteValueDictionary)	Gets the URL that corresponds to a set of route parameters and a route name. (Inherited from Control)
GetType()	Gets the Type of the current instance. (Inherited from Object)
GetUniqueIDRelativeTo(Control)	Returns the prefixed portion of the UniqueID property of the specified control. (Inherited from Control)
HasControls()	Determines if the server control contains any child controls. (Inherited from Control)
HasEvents()	Returns a value indicating whether events are registered for the control or any child controls. (Inherited from Control)
IsLiteralContent()	Determines if the server control holds only literal content. (Inherited from Control)
LoadControlState(Object)	Restores control-state information from a previous page request that was saved by the SaveControlState() method. (Inherited from Control)
LoadViewState(Object)	Loads the state of the values in the QueryExtender control that must be persisted.
MapPathSecure(String)	Retrieves the physical path that a virtual path, either absolute or relative, maps to. (Inherited from Control)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
OnBubbleEvent(Object, EventArgs)	Determines whether the event for the server control is passed up the page's UI server control hierarchy. (Inherited from Control)
OnDataBinding(EventArgs)	Raises the DataBinding event. (Inherited from Control)
OnInit(EventArgs)	Occurs when a new instance of the QueryExtender class is initialized.
OnLoad(EventArgs)	Raises the Load event. (Inherited from Control)
OnPreRender(EventArgs)	Raises the PreRender event. (Inherited from Control)
OnUnload(EventArgs)	Raises the Unload event. (Inherited from Control)
OpenFile(String)	Gets a Stream used to read a file. (Inherited from Control)
RaiseBubbleEvent(Object, EventArgs)	Assigns any sources of the event and its information to the control's parent. (Inherited from Control)
RemovedControl(Control)	Called after a child control is removed from the Controls collection of the Control object. (Inherited from Control)
Render(HtmlTextWriter)	Sends server control content to a provided HtmlTextWriter object, which writes the content to be rendered on the client. (Inherited from Control)
RenderChildren(HtmlTextWriter)	Outputs the content of a server control's children to a provided HtmlTextWriter object, which writes the content to be rendered on the client. (Inherited from Control)
RenderControl(HtmlTextWriter, ControlAdapter)	Outputs server control content to a provided HtmlTextWriter object using a provided ControlAdapter object. (Inherited from Control)
RenderControl(HtmlTextWriter)	Outputs server control content to a provided HtmlTextWriter object and stores tracing information about the control if tracing is enabled. (Inherited from Control)
ResolveAdapter()	Gets the control adapter responsible for rendering the specified control. (Inherited from Control)
ResolveClientUrl(String)	Gets a URL that can be used by the browser. (Inherited from Control)
ResolveUrl(String)	Converts a URL into one that is usable on the requesting client. (Inherited from Control)
SaveControlState()	Saves any server control state changes that have occurred since the time the page was posted back to the server. (Inherited from Control)
SaveViewState()	Saves the current view state of the QueryExtender control.
SetDesignModeState(IDictionary)	Sets design-time data for a control. (Inherited from Control)
SetRenderMethodDelegate(RenderMethod)	Assigns an event handler delegate to render the server control and its content into its parent control. (Inherited from Control)
SetTraceData(Object, Object, Object)	Sets trace data for design-time tracing of rendering data, using the traced object, the trace data key, and the trace data value. (Inherited from Control)
SetTraceData(Object, Object)	Sets trace data for design-time tracing of rendering data, using the trace data key and the trace data value. (Inherited from Control)
ToString()	Returns a string that represents the current object. (Inherited from Object)
TrackViewState()	Tracks view-state changes of the QueryExtender control so that the changes can be stored in the StateBag object for the control.

Events

DataBinding	Occurs when the server control binds to a data source. (Inherited from Control)
Disposed	Occurs when a server control is released from memory, which is the last stage of the server control lifecycle when an ASP.NET page is requested. (Inherited from Control)
Init	Occurs when the server control is initialized, which is the first step in its lifecycle. (Inherited from Control)
Load	Occurs when the server control is loaded into the Page object. (Inherited from Control)
PreRender	Occurs after the Control object is loaded but prior to rendering. (Inherited from Control)
Unload	Occurs when the server control is unloaded from memory. (Inherited from Control)

Explicit Interface Implementations

IControlBuilderAccessor.ControlBuilder	For a description of this member, see ControlBuilder. (Inherited from Control)
IControlDesignerAccessor.GetDesignModeState()	For a description of this member, see GetDesignModeState(). (Inherited from Control)
IControlDesignerAccessor.SetDesignModeState(IDictionary)	For a description of this member, see SetDesignModeState(IDictionary). (Inherited from Control)
IControlDesignerAccessor.SetOwnerControl(Control)	For a description of this member, see SetOwnerControl(Control). (Inherited from Control)
IControlDesignerAccessor.UserData	For a description of this member, see UserData. (Inherited from Control)
IDataBindingsAccessor.DataBindings	For a description of this member, see DataBindings. (Inherited from Control)
IDataBindingsAccessor.HasDataBindings	For a description of this member, see HasDataBindings. (Inherited from Control)
IExpressionsAccessor.Expressions	For a description of this member, see Expressions. (Inherited from Control)
IExpressionsAccessor.HasExpressions	For a description of this member, see HasExpressions. (Inherited from Control)
IParserAccessor.AddParsedSubObject(Object)	For a description of this member, see AddParsedSubObject(Object). (Inherited from Control)

Extension Methods

FindDataSourceControl(Control)	Returns the data source that is associated with the data control for the specified control.
FindFieldTemplate(Control, String)	Returns the field template for the specified column in the specified control's naming container.
FindMetaTable(Control)	Returns the metatable object for the containing data control.

See also

• QueryExpression
• ParameterDataSourceExpression
• SearchType