ICustomFunctionOperatorFormattable Interface

Defines server-side processing for custom functions.

Namespace: DevExpress.Data.Filtering

Assembly: DevExpress.Data.v20.2.dll

NuGet Packages: DevExpress.Data, DevExpress.WindowsDesktop.Data

Declaration

C#

public interface ICustomFunctionOperatorFormattable :
    ICustomFunctionOperator

VB.NET

Public Interface ICustomFunctionOperatorFormattable
    Inherits ICustomFunctionOperator

Related API Members

The following members return ICustomFunctionOperatorFormattable objects:

• ConnectionProviderSql.GetCustomFunctionOperator(String)

Remarks

Implement this interface in addition to the ICustomFunctionOperator interface to provide a database-specific SQL command for your custom function. This interface declares the functionality required to evaluate the custom function within criteria on the database server.

C#

public class SampleCustomOperatorFormattable : ICustomFunctionOperatorFormattable {
    public string Name => "CalcCost";
    public object Evaluate(params object[] operands) {
        return ((decimal)operands[0] * (int)operands[1]);
    }
    public string Format(Type providerType, params string[] operands) {
        if(typeof(PostgreSqlConnectionProvider).IsAssignableFrom(providerType)) {
            return $" {operands[0]} * {operands[1]} ";
        } else throw new NotSupportedException();
    }
    public Type ResultType(params Type[] operands) {
        return typeof(decimal);
    }
    public static SampleCustomOperatorFormattable Instance = new SampleCustomOperatorFormattable();
    public static void Register() {
        CriteriaOperator.RegisterCustomFunction(Instance);
    }
    public static void Unregister() {
        CriteriaOperator.UnregisterCustomFunction(Instance);
    }
}

VB.NET

Public Class SampleCustomOperatorFormattable
    Implements ICustomFunctionOperatorFormattable

    Public ReadOnly Property Name() As String
        Get
            Return "CalcCost"
        End Get
    End Property
    Public Function Evaluate(ParamArray ByVal operands() As Object) As Object
        Return (DirectCast(operands(0), Decimal) * DirectCast(operands(1), Integer))
    End Function
    Public Function Format(ByVal providerType As Type, ParamArray ByVal operands() As String) As String
        If GetType(PostgreSqlConnectionProvider).IsAssignableFrom(providerType) Then
            Return $" {operands(0)} * {operands(1)} "
        Else
            Throw New NotSupportedException()
        End If
    End Function
    Public Function ResultType(ParamArray ByVal operands() As Type) As Type
        Return GetType(Decimal)
    End Function
    Public Shared Instance As New SampleCustomOperatorFormattable()
    Public Shared Sub Register()
        CriteriaOperator.RegisterCustomFunction(Instance)
    End Sub
    Public Shared Sub Unregister()
        CriteriaOperator.UnregisterCustomFunction(Instance)
    End Sub
End Class

If you want to make your custom function available to end users in Expression Editors, implement the ICustomFunctionOperatorBrowsable interface as well.