ForeignKeyConverter Property (DataGridForeignKeyDescription)

Gets or sets a foreign key converter, which allows custom key/value mappings to be provided.

Syntax

Visual Basic
C#

'Declaration
 
Public Property ForeignKeyConverter As ForeignKeyConverter

'Usage
 
Dim instance As DataGridForeignKeyDescription
Dim value As ForeignKeyConverter
 
instance.ForeignKeyConverter = value
 
value = instance.ForeignKeyConverter

public ForeignKeyConverter ForeignKeyConverter {get; set;}

Property Value

A reference to a ForeignKeyConverter, which allows custom key/value mappings to be provided.

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.

Visual Basic

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

The following code provides the implementation of the PersonForeignKeyConverter 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;
 }
}

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

Reference

DataGridForeignKeyDescription Class
DataGridForeignKeyDescription Members