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PropertyExpression Class

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

Namespace:  System.Web.UI.WebControls.Expressions
Assembly:  System.Web.Extensions (in System.Web.Extensions.dll)

public class PropertyExpression : ParameterDataSourceExpression

The PropertyExpression type exposes the following members.

  NameDescription
Public methodPropertyExpressionInitializes a new instance of the PropertyExpression class.
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  NameDescription
Protected propertyContextGets the HttpContext instance of the owner control. (Inherited from DataSourceExpression.)
Public propertyDataSourceGets the data source object that is associated with the owner control. (Inherited from DataSourceExpression.)
Protected propertyIsTrackingViewStateGets a value that indicates whether a data source expression object is tracking its view state changes. (Inherited from DataSourceExpression.)
Protected propertyOwnerGets the owner control. (Inherited from DataSourceExpression.)
Public propertyParametersGets the parameters that are associated with this DataSourceExpression object. (Inherited from ParameterDataSourceExpression.)
Protected propertyViewStateGets an instance of the StateBag class that contains the current view state information. (Inherited from DataSourceExpression.)
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  NameDescription
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetQueryableApplies a PropertyExpression object by using the specified IQueryable data source object. (Overrides DataSourceExpression.GetQueryable(IQueryable).)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodLoadViewStateLoads the state of the values in the ParameterDataSourceExpression object that must be persisted. (Inherited from ParameterDataSourceExpression.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Protected methodSaveViewStateSaves the current view state of the ParameterDataSourceExpression object. (Inherited from ParameterDataSourceExpression.)
Public methodSetContextExecutes the expression by using the specified owner control, context, and data source. (Inherited from ParameterDataSourceExpression.)
Public methodSetDirtyMarks the DataSourceExpression object so that its state will be saved in view state. (Inherited from DataSourceExpression.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
Protected methodTrackViewStateTracks 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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  NameDescription
Explicit interface implemetationPrivate propertyIStateManager.IsTrackingViewStateWhen 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 implemetationPrivate methodIStateManager.LoadViewStateWhen implemented by a class, loads the previously saved view state of the data source expression object. (Inherited from DataSourceExpression.)
Explicit interface implemetationPrivate methodIStateManager.SaveViewStateWhen implemented by a class, saves the current view state of the DataSourceExpression object. (Inherited from DataSourceExpression.)
Explicit interface implemetationPrivate methodIStateManager.TrackViewStateWhen 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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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.

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>

.NET Framework

Supported in: 4.5, 4

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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