EditFormPage.ValidateCell Event

Occurs after a user changes a cell value in the default edit form and moves focus from the editor.

Namespace: DevExpress.Maui.DataGrid

Assembly: DevExpress.Maui.DataGrid.dll

NuGet Package: DevExpress.Maui.DataGrid

Declaration

public event EventHandler<ValidateCellEventArgs> ValidateCell

Event Data

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

Property	Description
ErrorContent	Gets or sets the validation error description.
FieldName	Returns the field name of the column that contains the cell whose value is being edited.
Item	Returns the data source object that is used to create the processed cell’s row.
NewValue	Returns the editor’s value.
OldValue	Returns the cell’s value before editing is started.
RowHandle	Returns the handle of the row that contains the cell whose value is being edited.

Example

This example shows how to validate cell values that users enter in the edit form.

You can verify each value after a user modifies it (in the default edit form only) or validate the entire form (default or custom) when a user closes it.

Validate a Value Once It Is Entered

Use the EditFormPage.ValidateCell event that occurs after a user changes a cell value in the default edit form and moves focus from the editor.

In the event hander:

1. Specify Validation Rules
   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.
2. Indicate an Error
   If the entered value fails validation, set the ErrorContent property to the validation error description.
   The edit form displays this text below the corresponding invalid value once a user moves focus from the current editor. The error is indicated and the edit form cannot be closed until the value is valid.
   Use the EditorErrorColor property to customize the color of error messages.

XAML

<dxg:DataGridView x:Name="grid" ItemsSource="{Binding Orders}" 
                  Tap="Grid_Tap">
    <!-- ... -->
</dxg:DataGridView>

C#

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

private void Grid_Tap(object sender, DataGridGestureEventArgs e) {
    if (e.Item != null) {
        var editForm = new EditFormPage(grid, grid.GetItem(e.RowHandle));
        editForm.ValidateCell += EditForm_ValidateCell;    
        Navigation.PushAsync(editForm);
    }
}

private void EditForm_ValidateCell(object sender, ValidateCellEventArgs e) {
    if (e.FieldName == "Quantity" && (decimal)e.NewValue <= 0) {
        e.ErrorContent = "The value must be positive.";
    }
    else if (e.FieldName == "Date" && (DateTime)e.NewValue > DateTime.Now.Date)
        e.ErrorContent = "The date value cannot be in the future.";
}

Validate Values When Closing the Edit Form

Use the EditFormPage.ValidateForm event that occurs after a user changes the values and tries to close the edit form.

In the event hander:

1. Specify Validation Rules
   Use the event parameter’s Values property to access all values that the form’s editors currently contain. Field names of the grid’s columns (FieldName) are keys in this dictionary.
2. Indicate errors
   If the entered value fails validation, add an error to the Errors dictionary with the corresponding column field as the key and the error description as the value.
   The default edit form automatically displays these errors below invalid values once a user tries to close the edit form. Each error is displayed until the corresponding value is corrected and the edit form cannot be closed until all values pass validation.
   If you create a custom view for the grid’s edit form, you can bind your template’s elements to the Errors collection to display validation errors.

XAML

<dxg:DataGridView x:Name="grid" ItemsSource="{Binding Orders}" 
                  Tap="Grid_Tap">
    <!-- ... -->
</dxg:DataGridView>

C#

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

private void Grid_Tap(object sender, DataGridGestureEventArgs e) {
    if (e.Item != null) {
        var editForm = new EditFormPage(grid, grid.GetItem(e.RowHandle));
        editForm.ValidateForm += EditForm_ValidateForm;
        Navigation.PushAsync(editForm);
    }
}

private void EditForm_ValidateForm(object sender, EditFormValidationEventArgs e) {
    if ((decimal)e.Values["Quantity"] <= 0) {
        e.Errors.Add("Quantity", "The value must be positive.");
    }
    if ((DateTime)e.Values["Date"] > DateTime.Now.Date)
        e.Errors.Add("Date", "The date value cannot be in the future.");
}