AppearanceAttribute.Criteria Property

Specifies the criteria string used when determining whether AppearanceAttribute.TargetItems should be affected by the conditional appearance rule generated from the current attribute.

Namespace: DevExpress.ExpressApp.ConditionalAppearance

Assembly: DevExpress.Persistent.Base.v21.2.dll

NuGet Package: DevExpress.Persistent.Base

Declaration

C#

public string Criteria { get; set; }

VB.NET

Public Property Criteria As String

Property Value

Type	Description
String	A string representing the criterion under which the conditional appearance rule is in effect.

Remarks

To learn how to declare string criteria and use Function Criteria Operators in string criteria, refer to the following articles:

• Ways to Build Criteria;
• Function Criteria Operators.

When you need to create a complex rule that cannot be specified using the Criteria property, you can implement a business class method that takes no parameters and returns a Boolean value specifying whether the rule is currently active (the Criteria will be ignored in this case). You do not need to specify the Method parameter when the AppearanceAttribute attribute is directly applied to the business class method. Refer to the Method property description for details.

Delayed Loading and Free Joins in Criteria Expressions

Avoid using Delayed Properties and Free Joins in a criteria expression, because AppearanceController calculates the expression during the paint process.

Delayed Properties and Free Joins may load data from the database during the paint process. This may cause UI flicks or corrupt the state of a WinForms control.

Use the following techniques to avoid side effects if you need to include Delayed Properties in a criteria expression:

• Add a calculated property to a business object and store the calculated value in the database. Refer to the following article for additional information: Calculate a Property Value Based on Values from a Detail Collection.
• Use the SetPrefetchPropertyNames(Object, String[]) method to pre-load collection properties before displaying data on the screen.

If the above techniques are not applicable and your app crashes with InvalidOperationException (‘Recursive read not allowed’ or ‘Entering the GetObjectsNonReenterant state is prohibited’), use the solution #4 from this article: Troubleshooting - How to resolve the “Entering the ‘GetObjectsNonReenterant’ state…” error.

Examples

Example 1

According to the rule demonstrated in the example below, the Category property in List Views will be displayed in Blue font color when its value is “Seafood”.

C#

using DevExpress.ExpressApp.ConditionalAppearance;
//...
[Appearance("CategoryColoredInListView", AppearanceItemType = "ViewItem", TargetItems = "Category",
 Criteria = "Category = 'Seafood'", Context = "ListView", FontColor = "Blue", Priority = 1)]
public class Product : BaseObject {
    public Product(Session session) : base(session) { }
    public Category Category {
        //...
    }
}
[DefaultProperty(nameof(Name))]
public class Category : BaseObject {
    public Category(Session session) : base(session) {}
    public string Name {
        //...
    }
}

VB.NET

Imports DevExpress.ExpressApp.ConditionalAppearance
'...
<Appearance("CategoryColoredInListView", AppearanceItemType := "ViewItem", TargetItems := "Category",
 Criteria := "Category = 'Seafood'", Context := "ListView", FontColor := "Blue", Priority := 1)> _
Public Class Product
        Inherits BaseObject
    Public Sub New(ByVal session As Session)
        MyBase.New(session)
    End Sub
    Public ReadOnly Property Category() As Category
        '...
    End Property
End Class
<DefaultProperty(NameOf(Name))> _
Public Class Category
        Inherits BaseObject
    Public Sub New(ByVal session As Session)
        MyBase.New(session)
    End Sub
    Public ReadOnly Property Name() As String
        '...
    End Property
End Class

Example 2

According to the rule demonstrated in the example below, a Product’s Deactivate Action will be hidden when the Status property is set to “Inactive” in all Product Views. Note that the Action ID specified in this rule contains the class name (“Product.Deactivate”), because the Deactivate Action is declared using the ActionAttribute. If an Action is declared in a Controller, specify its ID without the class name, e.g., “Delete” or “Unlink”.

C#

using DevExpress.ExpressApp.ConditionalAppearance;
//...
[Appearance("ActionVisibility", AppearanceItemType = "Action",
    TargetItems = "Product.Deactivate",
        Criteria = "Status = 'Inactive'", Context = "Any", Visibility = ViewItemVisibility.Hide)]
public class Product : BaseObject {
    public Product(Session session) : base(session) { }
    public ProductStatus Status {
        //...
    }   
    [Action(PredefinedCategory.RecordEdit, Caption = "Deactivate Product...", AutoCommit = true,
     TargetObjectsCriteria = "Status = 'Active'",
      SelectionDependencyType = MethodActionSelectionDependencyType.RequireSingleObject)]
    public void Deactivate() {
        Status = ProductStatus.Inactive;
    }
}

VB.NET

Imports DevExpress.ExpressApp.ConditionalAppearance
'...
<Appearance("ActionVisibility", AppearanceItemType := "Action", _
TargetItems := "Product.Deactivate", _
Criteria := "Status = 'Inactive'", Context := "Any", Visibility := ViewItemVisibility.Hide)> _
Public Class Product
        Inherits BaseObject
    Public Sub New(ByVal session As Session)
        MyBase.New(session)
    End Sub
    Public ReadOnly Property Status() As ProductStatus
        '...
    End Property
    <Action(PredefinedCategory.RecordEdit, Caption := "Deactivate Product...", AutoCommit := True,
    TargetObjectsCriteria := "Status = 'Active'", _
    SelectionDependencyType := MethodActionSelectionDependencyType.RequireSingleObject)> _
    Public Sub Deactivate()
        Status = ProductStatus.Inactive
    End Sub
End Class

You can find more examples in the Declare Conditional Appearance Rules in Code topic. See these examples in the Feature Center demo installed with the eXpressApp Framework in the %PUBLIC%\Documents\DevExpress Demos 21.2\Components\eXpressApp Framework\FeatureCenter folder, or refer to the Feature Center demo online.

Implements

Criteria