IsInstanceOfTypeFunction Class

A custom function that determines whether a particular object is of a specified type or derives from it.

Namespace: DevExpress.Xpo.Metadata

Assembly: DevExpress.Xpo.v24.1.dll

NuGet Packages: DevExpress.Win.PivotGrid, DevExpress.Win.TreeMap, DevExpress.Xpo

NuGet Package: DevExpress.Xpo

Declaration

C#

public class IsInstanceOfTypeFunction :
    ICustomFunctionOperatorBrowsable,
    ICustomFunctionOperator,
    ICustomFunctionDisplayAttributes,
    ICustomFunctionOperatorConvertibleToExpression,
    ICustomFunctionOperatorCompileable

VB.NET

Public Class IsInstanceOfTypeFunction
    Implements ICustomFunctionOperatorBrowsable,
               ICustomFunctionOperator,
               ICustomFunctionDisplayAttributes,
               ICustomFunctionOperatorConvertibleToExpression,
               ICustomFunctionOperatorCompileable

Remarks

This function is automatically registered in XPO applications. So, you can use it right from the start.

The IsInstanceOfTypeFunction custom function operator takes 2 operands:

1. The first operand specifies the object whose type will be checked.
2. The second operand specifies the fully qualified name of the required type.

Assume you have a collection of Employee objects. Employees can either be objects of the LocalEmployee, LocalTemporaryEmployee, or ForeignEmployee types:

C#

public class LocalEmployee : Employee { /* ... */ }

public class LocalTemporaryEmployee : LocalEmployee { /* ... */ }

public class ForeignEmployee : Employee { /* ... */ }

VB.NET

Public Class LocalEmployee
    Inherits Employee
    ' ...
End Class

Public Class LocalTemporaryEmployee
    Inherits LocalEmployee
    ' ...
End Class

Public Class ForeignEmployee
    Inherits Employee
    ' ...
End Class

The following code snippet demonstrates how the employees collection can be filtered to contain only local employees, including the temporary ones.

C#

using DevExpress.Xpo;
using DevExpress.Data.Filtering;
//...
XPCollection<EmployeeBase> employees = new XPCollection<EmployeeBase>(Session);
employees.Criteria = CriteriaOperator.Parse("IsInstanceOfType(This, ?)", typeof(LocalEmployee).FullName);

VB.NET

Imports DevExpress.Xpo
Imports DevExpress.Data.Filtering
'...
Private employees As New XPCollection(Of EmployeeBase)(Session)
employees.Criteria = CriteriaOperator.Parse("IsInstanceOfType(This, ?)", GetType(LocalEmployee).FullName)

The IsInstanceOfTypeFunction function is automatically registered in XPO applications.

Inheritance

Object

IsInstanceOfTypeFunction