public event InvalidRowExceptionEventHandler InvalidRowException

Public Event InvalidRowException As InvalidRowExceptionEventHandler

<dxg:GridControl x:Name="grid" AutoGenerateColumns="AddNew">
    <dxg:GridControl.View>
        <dxg:TableView AutoWidth="True"
                       ValidateRow="OnValidateRow"
                       InvalidRowException="OnInvalidRowException"/>
    </dxg:GridControl.View>
</dxg:GridControl>

public class Task : IDataErrorInfo {
    public string TaskName { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }

    string IDataErrorInfo.Error => StartDate > EndDate ? "Either Start Date or End Date should be corrected." : null;
    string IDataErrorInfo.this[string columnName] {
        get {
            switch(columnName) {
                case nameof(StartDate):
                    if(StartDate > EndDate)
                        return "Start Date must be less than End Date";
                    break;
                case nameof(EndDate):
                    if(StartDate > EndDate)
                        return "End Date must be greater than Start Date";
                    break;
                case nameof(TaskName):
                    if(string.IsNullOrEmpty(TaskName))
                        return "Enter a task name";
                    break;
            }
            return null;
        }
    }
}
public partial class MainWindow : Window {
// ...
    void OnValidateRow(object sender, GridRowValidationEventArgs e) {
        var task = (Task)e.Row;
        if(task.StartDate > task.EndDate)
            e.SetError("Start Date must be less than End Date");
        if(string.IsNullOrEmpty(task.TaskName))
            e.SetError("Enter a task name");
    }

    void OnInvalidRowException(object sender, InvalidRowExceptionEventArgs e) {
        e.ExceptionMode = ExceptionMode.NoAction;
    }
}

Public Class Task
    Implements IDataErrorInfo

    Public Property TaskName As String

    Public Property StartDate As Date

    Public Property EndDate As Date

    Private ReadOnly Property [Error] As String Implements IDataErrorInfo.[Error]
        Get
            Return If(StartDate > EndDate, "Either Start Date or End Date should be corrected.", Nothing)
        End Get
    End Property

    Private ReadOnly Property Item(ByVal columnName As String) As String Implements IDataErrorInfo.Item
        Get
            Select Case columnName
                Case NameOf(Task.StartDate)
                    If StartDate > EndDate Then Return "Start Date must be less than End Date"
                Case NameOf(Task.EndDate)
                    If StartDate > EndDate Then Return "End Date must be greater than Start Date"
                Case NameOf(Task.TaskName)
                    If String.IsNullOrEmpty(TaskName) Then Return "Enter a task name"
            End Select

            Return Nothing
        End Get
    End Property
End Class

Public Partial Class MainWindow
    Inherits Window
' ...
    Private Sub OnValidateRow(ByVal sender As Object, ByVal e As GridRowValidationEventArgs)
        Dim task = CType(e.Row, Task)
        If task.StartDate > task.EndDate Then e.SetError("Start Date must be less than End Date")
        If String.IsNullOrEmpty(task.TaskName) Then e.SetError("Enter a task name")
    End Sub

    Private Sub OnInvalidRowException(ByVal sender As Object, ByVal e As InvalidRowExceptionEventArgs)
        e.ExceptionMode = ExceptionMode.NoAction
    End Sub
End Class

ValidateRow="OnValidateRow"
                   InvalidRowException="OnInvalidRowException" />
</dxg:GridControl.View>

ValidateRow="OnValidateRow"
                   InvalidRowException="OnInvalidRowException"/>
</dxg:GridControl.View>