How to remove the top-right corner error mark from the GridCell by pressing Esc key when validated by handling the CurrentCellValidating event?

In the SfDataGrid, validation can be done by handling the CurrentCellValidating event. The SfDataGrid does not allow the end-user to move to the other cells until the validation succeeds. In a meantime, you can move to the other cells after pressing Esc key that resets the validation status and error message at the top-right corner.

//Handles the CurrentCellValidating event.
SfdataGrid.CurrentCellValidating += SfdataGrid_CurrentCellValidating;
void SfdataGrid_CurrentCellValidating(object sender, CurrentCellValidatingEventArgs args)
{
    if (args.Column.MappingName == "EmployeeSalary" && Convert.ToDouble(args.NewValue) < 20000)
    {
        args.ErrorMessage = "EmployeeSalary should not less than 20000";
        args.IsValid = false;
    }
}

It is possible to reset the validation status when the end-user presses Esc key from the edit mode by overriding the GridSelectionController. In the following code example, the validation status and top-right corner error indication is reset by invoking the ValidationHelper.ResetValidations method on pressing the Esc key by overriding the ProcessKeyDown method of the GridSelectionController.

For WPF:

using Syncfusion.UI.Xaml.Grid;
using Syncfusion.UI.Xaml.Grid.Helpers;
// Sets the instance of the customized GridSelectionController class to the SfDataGird.SelectionController property.
SfdataGrid.SelectionController = new GridSelectionControllerExt(SfdataGrid);
public class GridSelectionControllerExt : GridSelectionController
{
    public GridSelectionControllerExt(SfDataGrid dataGrid)
        : base(dataGrid)
    {
    }
    protected override void ProcessKeyDown(KeyEventArgs args)
    {
        if (this.CurrentCellManager.HasCurrentCell && this.CurrentCellManager.CurrentCell.IsEditing && args.Key == Key.Escape)
        {
            var helper = DataGrid.GetValidationHelper();
            MethodInfo[] methodInfos = typeof(ValidationHelper).GetMethods(BindingFlags.NonPublic | BindingFlags.Instance);
            // Gets the ResetValidations method by using reflection.
            var resetValidation = methodInfos.FirstOrDefault(item => item.Name == "ResetValidations");
            resetValidation.Invoke(helper, new object[] { true });
            this.CurrentCellManager.EndEdit(false);
            return;
        }
        base.ProcessKeyDown(args);
    }
}

For WinRT:

public class GridSelectionControllerExt : GridSelectionController
{
    public GridSelectionControllerExt(SfDataGrid dataGrid)
        : base(dataGrid)
    {
    }
    protected override void ProcessKeyDown(KeyRoutedEventArgs args)
    {     
        if (this.CurrentCellManager.HasCurrentCell && this.CurrentCellManager.CurrentCell.IsEditing && args.Key == VirtualKey.Escape)
        {
            var helper = DataGrid.GetValidationHelper();
            // Gets the ResetValidations method by using reflection.
            foreach (var method in helper.GetType().GetRuntimeMethods())
            {
                if (method.Name.Equals("ResetValidations"))
                {
                    method.Invoke(helper, new object[] { true });
                    this.CurrentCellManager.EndEdit(false);
                    return;
                }
            }      
        }
        base.ProcessKeyDown(args);
    }
}

Note:

You need to override the GridCellSelectionController class when the SelectionUnit is GridSelecionUnit.Cell.

The corner error mark is enabled when the employeesalary less 20000 as shown in following screenshot

employeeSalary