How to: Validate Data Rows and Indicate Errors

• Jun 07, 2019
• 5 minutes to read

This example shows how to check the validity of data entered by end users into a data row. The GridViewBase.ValidateRow and GridViewBase.InvalidRowException events are handled to validate the focused row’s data, and if it is invalid, prevent the row focus from being moved to another row until invalid values are corrected.

Since the Task class does not support error notifications, it implements the IDXDataErrorInfo interface, providing two members to get error descriptions for the entire row and for individual cells (data source fields). This displays error icons within cells with invalid values. Pointing to such an error icon displays a tooltip with an error description.

View Example

Window1.xaml

<Window x:Class="DXGrid_ValidateRow.Window1" 
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:dxg="http://schemas.devexpress.com/winfx/2008/xaml/grid" 
    Title="Window1" Height="300" Width="500">
    <Grid>
        <dxg:GridControl x:Name="grid">
            <dxg:GridControl.Columns>
                <dxg:GridColumn FieldName="TaskName" />
                <dxg:GridColumn FieldName="StartDate" />
                <dxg:GridColumn FieldName="EndDate" />
            </dxg:GridControl.Columns>
            <dxg:GridControl.View>
                <dxg:TableView AutoWidth="True" 
                               ValidateRow="TableView_ValidateRow" 
                               InvalidRowException="TableView_InvalidRowException" />
            </dxg:GridControl.View>
        </dxg:GridControl>
    </Grid>
</Window>

Window1.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Data;
using DevExpress.Xpf.Grid;
using DevExpress.XtraEditors.DXErrorProvider;

namespace DXGrid_ValidateRow {
    public partial class Window1 : Window {
        public Window1() {
            InitializeComponent();
            grid.ItemsSource = TaskList.GetData();
        }

        private void TableView_ValidateRow(object sender, GridRowValidationEventArgs e) {
            DateTime startDate = ((Task)e.Row).StartDate;
            DateTime endDate = ((Task)e.Row).EndDate;
            e.IsValid = startDate < endDate;
        }

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

    public class TaskList {
        public static List<Task> GetData() {
            List<Task> data = new List<Task>();
            data.Add(new Task() { TaskName = "Complete Project A",
                StartDate = new DateTime(2009, 7, 17), EndDate = new DateTime(2009, 7, 10) });
            data.Add(new Task() { TaskName = "Test Website",
                StartDate = new DateTime(2009, 7, 10), EndDate = new DateTime(2009, 7, 12) });
            data.Add(new Task() { TaskName = "Publish Docs",
                StartDate = new DateTime(2009, 7, 4), EndDate = new DateTime(2009, 7, 6) });
            return data;
        }
    }

    public class Task : IDXDataErrorInfo {
        public string TaskName { get; set; }
        public DateTime StartDate { get; set; }
        public DateTime EndDate { get; set; }
        void IDXDataErrorInfo.GetError(ErrorInfo info) {
            if (StartDate > EndDate) {
                SetErrorInfo(info,
                    "Either StartDate or EndDate should be corrected.",
                    ErrorType.Critical);
            }
        }
        void IDXDataErrorInfo.GetPropertyError(string propertyName, ErrorInfo info) {
            switch (propertyName) {
                case "StartDate":
                    if (StartDate > EndDate)
                        SetErrorInfo(info,
                            "StartDate must be less than EndDate",
                            ErrorType.Critical);
                    break;
                case "EndDate":
                    if (StartDate > EndDate)
                        SetErrorInfo(info,
                            "EndDate must be greater than StartDate",
                            ErrorType.Critical);
                    break;
                case "TaskName":
                    if (IsStringEmpty(TaskName))
                        SetErrorInfo(info,
                            "Task name hasn't been entered",
                            ErrorType.Information);
                    break;
            }
        }
        void SetErrorInfo(ErrorInfo info, string errorText, ErrorType errorType) {
            info.ErrorText = errorText;
            info.ErrorType = errorType;
        }
        bool IsStringEmpty(string str) {
            return (str != null && str.Trim().Length == 0);
        }
    }
}

Window1.xaml.vb

Imports Microsoft.VisualBasic
Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Data
Imports System.Windows.Documents
Imports System.Windows.Input
Imports System.Windows.Media
Imports System.Windows.Media.Imaging
Imports System.Windows.Navigation
Imports System.Windows.Shapes
Imports System.Data
Imports DevExpress.XtraEditors.DXErrorProvider

Namespace DXGrid_ValidateRow
    Partial Public Class Window1
        Inherits Window
        Public Sub New()
            InitializeComponent()
            grid.ItemsSource = TaskList.GetData()
        End Sub

        Private Sub TableView_ValidateRow(ByVal sender As Object, _
            ByVal e As DevExpress.Xpf.Grid.GridRowValidationEventArgs)
                Dim startDate As DateTime = (CType(e.Row, Task)).StartDate
                Dim endDate As DateTime = (CType(e.Row, Task)).EndDate
                e.IsValid = startDate < endDate
        End Sub

        Private Sub TableView_InvalidRowException(ByVal sender As Object, _
            ByVal e As DevExpress.Xpf.Grid.InvalidRowExceptionEventArgs)
                e.ExceptionMode = DevExpress.Xpf.Grid.ExceptionMode.NoAction
        End Sub
    End Class

    Public Class TaskList
        Public Shared Function GetData() As List(Of Task)
            Dim data As New List(Of Task)()
            data.Add(New Task() With {.TaskName = "Complete Project A", _
                .StartDate = New DateTime(2009, 7, 17), .EndDate = New DateTime(2009, 7, 10)})
            data.Add(New Task() With {.TaskName = "Test Website", _
                .StartDate = New DateTime(2009, 7, 10), .EndDate = New DateTime(2009, 7, 12)})
            data.Add(New Task() With {.TaskName = "Publish Docs", _
                .StartDate = New DateTime(2009, 7, 4), .EndDate = New DateTime(2009, 7, 6)})
            Return data
        End Function
    End Class

    Public Class Task
        Implements IDXDataErrorInfo
        Private privateTaskName As String
        Public Property TaskName() As String
            Get
                Return privateTaskName
            End Get
            Set(ByVal value As String)
                privateTaskName = value
            End Set
        End Property
        Private privateStartDate As DateTime
        Public Property StartDate() As DateTime
            Get
                Return privateStartDate
            End Get
            Set(ByVal value As DateTime)
                privateStartDate = value
            End Set
        End Property
        Private privateEndDate As DateTime
        Public Property EndDate() As DateTime
            Get
                Return privateEndDate
            End Get
            Set(ByVal value As DateTime)
                privateEndDate = value
            End Set
        End Property
        Private Sub GetError(ByVal info As ErrorInfo) Implements IDXDataErrorInfo.GetError
            If StartDate > EndDate Then
                SetErrorInfo(info, _
                    "Either StartDate or EndDate should be corrected.", _
                    ErrorType.Critical)
            End If
        End Sub
        Private Sub GetPropertyError(ByVal propertyName As String, _
            ByVal info As ErrorInfo) Implements IDXDataErrorInfo.GetPropertyError
                Select Case propertyName
                    Case "StartDate"
                        If StartDate > EndDate Then
                            SetErrorInfo(info, _
                                "StartDate must be less than EndDate", _
                                ErrorType.Critical)
                        End If
                    Case "EndDate"
                        If StartDate > EndDate Then
                            SetErrorInfo(info, _
                                "EndDate must be greater than StartDate", _
                                ErrorType.Critical)
                        End If
                    Case "TaskName"
                        If IsStringEmpty(TaskName) Then
                            SetErrorInfo(info, _
                                "Task name hasn't been entered", _
                                ErrorType.Information)
                        End If
                End Select
        End Sub
        Private Sub SetErrorInfo(ByVal info As ErrorInfo, _
            ByVal errorText As String, _
            ByVal errorType As ErrorType)
                info.ErrorText = errorText
                info.ErrorType = errorType
        End Sub
        Private Function IsStringEmpty(ByVal str As String) As Boolean
            Return (str IsNot Nothing AndAlso str.Trim().Length = 0)
        End Function
    End Class
End Namespace