Xceed DataGrid for WPF v7.3 Documentation
Xceed.Wpf.DataGrid Assembly / Xceed.Wpf.DataGrid Namespace / ForeignKeyConverter Class
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    ForeignKeyConverter Class
    In This Topic

    Represents a foreign key converter, which allows custom key/value mappings to be provided.

    Syntax
    'Declaration
     
    Public MustInherit Class ForeignKeyConverter 
    'Usage
     
    Dim instance As ForeignKeyConverter
    public abstract class ForeignKeyConverter 
    Remarks

    By default, foreign key constraints defined by a DataTable or DataView as well as enums can be automatically detected; however, through a ForeignKeyConverter, custom key/value mappings can also be defined. When providing custom key/value mappings, a foreign key converter must be created by deriving from the ForeignKeyConverter class and overriding its GetKeyFromValue and GetValueFromKey methods in which the value for a specified key and the key for a specified value should be returned (see implementation of PersonForeignKeyConverter class in Example 2). This converter can then be provided to the ForeignKeyConverter property of either a foreign key description or configuration.

    If a ForeignKeyConverter has not been explicitly provided for a ForeignKeyConfiguration, the converter from its corresponding DataGridForeignKeyDescription will be used.

    Example
    The following code provides the implementation of the PersonForeignKeyConverter class. The following code provides the implementation of the PersonForeignKeyConverter class.
    Public Class PersonForeignKeyConverter
                 Inherits ForeignKeyConverter
    
      Public Overrides Function GetKeyFromValue( value As Object, configuration As ForeignKeyConfiguration ) As Object
        Dim bindingList As PersonBindingList = TryCast( configuration.ItemsSource, PersonBindingList )
        If Not bindingList Is Nothing Then
          Dim person As Person = TryCast( value, Person )
          If Not person Is Nothing Then
            Return person.PersonID
          End If
        End If
        Return -1
      End Function
      Public Overrides Function GetValueFromKey( key As Object, configuration As ForeignKeyConfiguration ) As Object
       Dim bindingList As PersonBindingList = TryCast( configuration.ItemsSource, PersonBindingList )
        If Not bindingList Is Nothing Then
          Try
            Dim personID As Integer = CInt( key )
            Dim person As Person
            For Each person In bindingList
              If person.PersonID = personID Then
                Return person
              End If
            Next person
          Catch e As Exception
            ' key can be nothing
          End Try
        Return Nothing
      End Function
    End Class
    public class PersonForeignKeyConverter : ForeignKeyConverter
    {
     public override object GetKeyFromValue( object value, ForeignKeyConfiguration configuration )
     {
       PersonBindingList bindingList = configuration.ItemsSource as PersonBindingList;
       if( bindingList != null )
       {
         Person person = value as Person;
         if( person != null )
         {
           return person.PersonID;
         }
       }
       return -1;
     }
     public override object GetValueFromKey( object key, ForeignKeyConfiguration configuration )
     {
       PersonBindingList bindingList = configuration.ItemsSource as PersonBindingList;
       if( bindingList != null )
       {
         try
         {
           int personID = ( int )key;
           foreach( Person person in bindingList )
           {
             if( person.PersonID == personID )
             {
               return person;
             }
           }
         }
         catch( Exception )
         {
           // key can be null
         }
       }
       return null;
     }
    }
    Inheritance Hierarchy
    Requirements

    Target Platforms: Windows 11, Windows 10, 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

    See Also