DataGridView.ValidationError Event

Occurs when a value in the in-place cell editor fails validation or when it cannot be saved to a data source.

Namespace: DevExpress.Maui.DataGrid

Assembly: DevExpress.Maui.DataGrid.dll

NuGet Package: DevExpress.Maui.DataGrid

Declaration

public event EventHandler<ValidationErrorEventArgs> ValidationError

Event Data

The ValidationError event's data class is ValidationErrorEventArgs. The following properties provide information specific to this event:

Property	Description
ErrorContent	Gets or sets the validation error description.

Example

This example shows how to validate a new cell value when a user modified it in an in-place cell editor and moves focus to another cell.

The DataGridView instance is bound to a collection of orders, and its Quantity column allows users to enter positive numbers only. If a new cell value does not pass validation, an error message is displayed and the user cannot move focus to another cell until the error is corrected.

Follow the steps below to validate cell values:

1. Specify Validation Rules
   Subscribe to the DataGridView.ValidateCell event, and implement validation logic in the event handler.
   Use the event parameter’s OldValue and NewValue properties to get the cell’s original and new value (the value that should be validated). The FieldName and RowHandle properties allow you to obtain the column and row that contain the cell whose value is being edited.
   If a cell value fails validation, set the ErrorContent property to the string that describes the validation error. A user cannot move focus to another cell until the error is fixed and the ErrorContent string is empty.
2. Indicate Errors
   Handle the DataGridView.ValidationError event to provide a response to entering invalid data (for example, show validation error message to users). This event parameter’s ValidationErrorEventArgs.ErrorContent property contains the error description assigned to the ValidateCellEventArgs.ErrorContent property in the ValidateCell event handler.

XAML

<dxg:DataGridView x:Name="grid" ItemsSource="{Binding Orders}" 
                  ValidateCell="Grid_ValidateCell"
                  ValidationError="Grid_ValidationError">
    <!-- ... -->
</dxg:DataGridView>

C#

using Microsoft.Maui.Controls;
using DevExpress.Maui.DataGrid;
// ...

private void Grid_ValidateCell(object sender, ValidateCellEventArgs e) {
    if (e.FieldName == "Quantity" && (decimal)e.NewValue <= 0) 
        e.ErrorContent = "The value must be positive.";
}

private void Grid_ValidationError(object sender, ValidationErrorEventArgs e) {
    DisplayAlert("Input Error", e.ErrorContent, "OK");
}