CellValidationRule Class
See Also  Members   Example 
Xceed.Wpf.DataGrid Assembly > Xceed.Wpf.DataGrid.ValidationRules Namespace : CellValidationRule Class

Represents a rule that validates cell content.

Syntax

Visual Basic (Declaration) 
Public MustInherit Class CellValidationRule
C# 
public abstract class CellValidationRule

Example

All examples in this topic assume that the grid is bound to a list of Composer objects, unless stated otherwise.

The following example demonstrates how to create a custom CellValidationRule and add it to a column's CellValidationRules collection to provide UI-level validation.
XAMLCopy Code
<Grid xmlns:xcdg="http://schemas.xceed.com/wpf/xaml/datagrid" 
     xmlns:local="clr-namespace:Xceed.Wpf.Documentation"> 
  <Grid.Resources> 
     <xcdg:DataGridCollectionViewSource x:Key="cvs_composers" 
                                        Source="{Binding Source={x:Static Application.Current}, 
                                                         Path=Composers}"/> 
     <!--A data provider to bind to the Period enum--> 
     <ObjectDataProvider x:Key="periods" 
                         MethodName="GetValues" 
                         ObjectType="{x:Type local:Period}"> 
        <ObjectDataProvider.MethodParameters> 
           <x:Type TypeName="local:Period"/> 
        </ObjectDataProvider.MethodParameters> 
     </ObjectDataProvider> 
     <!--A cell editor that will be used to edit a Period column with a combo box--> 
     <xcdg:CellEditor x:Key="periodEditor"> 
        <xcdg:CellEditor.EditTemplate> 
           <DataTemplate> 
              <ComboBox BorderThickness="0" 
                        MinHeight="22" 
                        VerticalContentAlignment="Top" 
                        SelectedValuePath="." 
                        ItemsSource="{Binding Source={StaticResource periods}}" 
                        SelectedValue="{xcdg:CellEditorBinding}"> 
                 <ComboBox.Resources> 
                    <Style TargetType="Popup"> 
                       <Setter Property="TextElement.Foreground" 
                               Value="{DynamicResource {x:Static SystemColors.WindowTextBrushKey}}" /> 
                    </Style> 
                 </ComboBox.Resources> 
              </ComboBox> 
           </DataTemplate> 
        </xcdg:CellEditor.EditTemplate> 
     </xcdg:CellEditor> 
  </Grid.Resources> 
  <xcdg:DataGridControl ItemsSource="{Binding Source={StaticResource cvs_composers}}" 
                        UpdateSourceTrigger="RowEndingEdit"> 
     <xcdg:DataGridControl.Columns> 
       <xcdg:Column FieldName="Period" 
                    CellEditor="{StaticResource periodEditor}">                                    
          <xcdg:Column.CellValidationRules> 
             <local:PeriodVSCompositionCountCellValidationRule/> 
          </xcdg:Column.CellValidationRules> 
       </xcdg:Column> 
       <xcdg:Column FieldName="CompositionCount"> 
          <xcdg:Column.CellValidationRules> 
             <local:PeriodVSCompositionCountCellValidationRule /> 
          </xcdg:Column.CellValidationRules> 
       </xcdg:Column> 
     </xcdg:DataGridControl.Columns> 
  </xcdg:DataGridControl> 
</Grid>
Implementation of the PeriodVSCompositionCountCellValidationRule validation rule. Implementation of the Person class can be found in the Validating Data topic.
Visual BasicCopy Code
Imports System
Imports Xceed.Wpf.DataGrid.ValidationRules
Imports Xceed.Wpf.DataGrid
Imports System.Globalization
Imports System.Windows.Controls
Namespace Xceed.Wpf.Documentation

  Public Class PeriodVSCompositionCountCellValidationRule
               Inherits CellValidationRule

    Public Overrides Function Validate( ByVal value As Object, ByVal culture As CultureInfo, _
                                        ByVal context As CellValidationContext ) As ValidationResult

      Dim parentRow As Row = context.Cell.ParentRow
      Dim compositionCount As Integer
      Dim period As Period
      If context.Cell.FieldName = "Period" Then
        period = CType( value, Period )
        compositionCount = CInt( parentRow.Cells( "CompositionCount" ).Content )
      Else
        period = CType( parentRow.Cells( "Period" ).Content, Period )
        compositionCount = CInt( value )
      End If
      If( ( period = Period.Modern ) And ( compositionCount > 40 ) ) Then
        Return New ValidationResult( False, "Composition count must be less than 50 when the period is set to Modern." );
      End If
      Return ValidationResult.ValidResult
    End Function
  End Class
End Namespace
Implementation of the PeriodVSCompositionCountCellValidationRule validation rule. Implementation of the Person class can be found in the Validating Data topic.
C#Copy Code
using System;
using Xceed.Wpf.DataGrid.ValidationRules;
using Xceed.Wpf.DataGrid;
using System.Globalization;
using System.Windows.Controls;
namespace Xceed.Wpf.Documentation
{
 public class PeriodVSCompositionCountCellValidationRule : CellValidationRule
{
  public override ValidationResult Validate( object value, CultureInfo culture,
                                             CellValidationContext context )
  {
    Row parentRow = context.Cell.ParentRow;
    int compositionCount;
    Period period;
    if( context.Cell.FieldName == "Period" )
    {
      period = ( Period )value;       
      compositionCount = ( int )parentRow.Cells[ "CompositionCount" ].Content;
    }
    else
    {
      period = ( Period )parentRow.Cells[ "Period" ].Content;
      compositionCount = ( int )value;
    }
    if( ( period == Period.Modern ) && compositionCount > 40 )
      return new ValidationResult( false, "Composition count must be less than 50 when the period is set to Modern." );
    return ValidationResult.ValidResult;
  }
}
}

Remarks

When the value of a cell fails the validation process, its HasValidationError property will return true and its ValidationError property will contain a CellValidationError, which provides information on the cell in error, the error content, the exception (if one was thrown), and the validation rule that failed.  If the validation rule that failed is a binding-level ValidationRule, it will be wrapped in a PassthroughCellValidationRule. Validation errors will also be reported by a row when the value of one or more of its cells fails the validation process. Like cells, when a row contains validation errors, its HasValidationError property will return true and its ValidationError property will contain a RowValidationError, which provides information on the row in error, the error content, the exception, and the validation rule that failed.

Notes

Any validation rule created from the ValidationRule class can be reused in a grid by using a  PassthroughCellValidationRule, which wraps any validation rule and exposes it as a CellValidationRule.

Inheritance Hierarchy

Requirements

Supported Operating Systems: Windows Server 2003 Service Pack 1; Windows Vista; Windows XP Service Pack 2

See Also