PropertyExpression Class (System.Web.UI.WebControls.Expressions)

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Classic
Lightweight
ScriptFree
.NET Framework Class Library
PropertyExpression Class

Provides a way to create a Where clause from parameters in a WhereParameters collection.

Inheritance Hierarchy
System.Object
  System.Web.UI.WebControls.Expressions.DataSourceExpression
    System.Web.UI.WebControls.Expressions.ParameterDataSourceExpression
      System.Web.UI.WebControls.Expressions.PropertyExpression

Namespace:  System.Web.UI.WebControls.Expressions
Assembly:  System.Web.Extensions (in System.Web.Extensions.dll)
Syntax
Visual Basic
Public Class PropertyExpression _
	Inherits ParameterDataSourceExpression
C#
public class PropertyExpression : ParameterDataSourceExpression
Visual C++
public ref class PropertyExpression : public ParameterDataSourceExpression
F#
type PropertyExpression =  
    class
        inherit ParameterDataSourceExpression
    end

The PropertyExpression type exposes the following members.

Constructors
  Name Description
Public method PropertyExpression Initializes a new instance of the PropertyExpression class.
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Properties
  Name Description
Protected property Context Gets the HttpContext instance of the owner control. (Inherited from DataSourceExpression.)
Public property DataSource Gets the data source object that is associated with the owner control. (Inherited from DataSourceExpression.)
Protected property IsTrackingViewState Gets a value that indicates whether a data source expression object is tracking its view state changes. (Inherited from DataSourceExpression.)
Protected property Owner Gets the owner control. (Inherited from DataSourceExpression.)
Public property Parameters Gets the parameters that are associated with this DataSourceExpression object. (Inherited from ParameterDataSourceExpression.)
Protected property ViewState Gets an instance of the StateBag class that contains the current view state information. (Inherited from DataSourceExpression.)
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Methods
  Name Description
Public method Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method GetQueryable Applies a PropertyExpression object by using the specified IQueryable data source object. (Overrides DataSourceExpression.GetQueryable(IQueryable).)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Protected method LoadViewState Loads the state of the values in the ParameterDataSourceExpression object that must be persisted. (Inherited from ParameterDataSourceExpression.)
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Protected method SaveViewState Saves the current view state of the ParameterDataSourceExpression object. (Inherited from ParameterDataSourceExpression.)
Public method SetContext Executes the expression by using the specified owner control, context, and data source. (Inherited from ParameterDataSourceExpression.)
Public method SetDirty Marks the DataSourceExpression object so that its state will be saved in view state. (Inherited from DataSourceExpression.)
Public method ToString Returns a string that represents the current object. (Inherited from Object.)
Protected method TrackViewState Tracks view-state changes of the ParameterDataSourceExpression object so that the changes can be stored in the StateBag object for the object. (Inherited from ParameterDataSourceExpression.)
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Explicit Interface Implementations
  Name Description
Explicit interface implemetation Private property IStateManager.IsTrackingViewState When implemented by a class, gets a value that indicates whether a data source expression object is tracking its view state changes. (Inherited from DataSourceExpression.)
Explicit interface implemetation Private method IStateManager.LoadViewState When implemented by a class, loads the previously saved view state of the data source expression object. (Inherited from DataSourceExpression.)
Explicit interface implemetation Private method IStateManager.SaveViewState When implemented by a class, saves the current view state of the DataSourceExpression object. (Inherited from DataSourceExpression.)
Explicit interface implemetation Private method IStateManager.TrackViewState When implemented by a class, tracks view state changes of the DataSourceExpression object so that the changes can be stored in the StateBag object for the data source expression object. (Inherited from DataSourceExpression.)
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Remarks

The PropertyExpression class is used with the QueryExtender control to filter data in data fields. The PropertyExpression class compares a property value of a column to a specified value. For example, you can compare a Boolean value to the value in the discontinued column of a Products table in a database.

The PropertyExpression class creates an equals (==) comparison for the value of each parameter and the corresponding property of the IQueryable data object. If you provide more than one parameter, the parameters are combined using the logical AND operator. Parameters that contain an empty value are not added to the Where clause.

Examples

The following example shows how to search the Products table of the AdventureWorks database for products whose MakeFlag property (a Boolean column) is set to true. The Boolean value parameter is set in a check box. The result of the query that is returned from the LinqDataSource control is displayed in a GridView control.

This code example is part of a larger example that is provided in Walkthrough: Filtering Data in a Web Page Using Declarative Syntax.


<form id="form1" runat="server">
  Make More: <asp:CheckBox ID="MakeCheckBox" runat="server" />

  <asp:LinqDataSource ID="LinqDataSource1"  
      ContextTypeName="FilterDemo.AdventureWorksDataContext"  
      TableName="Products" runat="server"> 
  </asp:LinqDataSource>

  <asp:QueryExtender runat="server"    
      TargetControlID="LinqDataSource1">
    <asp:PropertyExpression>
      <asp:ControlParameter ControlID="MakeCheckBox" Name="MakeFlag" />
    </asp:PropertyExpression>
  </asp:QueryExtender>

  <asp:GridView ID="GridView1" runat="server"  
      DataSourceID="LinqDataSource1" AllowPaging="True"    
      DataKeyNames="ProductID>
  </asp:GridView>
</form>
Version Information

.NET Framework

Supported in: 4
Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Thread Safety
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
See Also

Reference

System.Web.UI.WebControls.Expressions Namespace

Other Resources

QueryExtender Web Server Control Overview
Walkthrough: Filtering Data in a Web Page Using Declarative Syntax