WPF VALIDATION - MANOHAR GOUD 9866550012

K MANOHAR GOUD

9866550012

WPF validation There are too many ways to validate the WPF controlls. I explain here some of them with example.  We need a validation to prevent user from entering a wrong details. Here we used IDataErrorInfo for validation.Validation made easy with IDataErrorInfo. here I explain you how we used IDataErrorInfo in WPF for validating the controlls. If we are using binding property to bind the contrlss with the properties then IDataErrorInfo is a very easy to use.I go through with most of the post but they not provide the combobox validation but here I explain the combobox validation also First we need to create a class with some properties to test and list for binding the comboboxes We create a class "Student" which inherit with IDataErrorInfo

class Student : IDataErrorInfo

    {

        public string FirstName { get; set; }

        public int RollNumber { get; set; }

        public string Division { get; set; }

        public List<string> Divisions { get; set; }

        public string Error

        {

            get { throw new NotImplementedException(); }

        }

        public string this[string columnName]

        {

            get

            {

                string result = null;

                if (columnName == "FirstName")

                {

                    if (string.IsNullOrEmpty(FirstName) || FirstName.Length < 3)

                        result = "Please enter a Name";

                }

                if (columnName == "RollNumber")

                {

                    if (RollNumber <= 0)

                        result = "Please enter a Proper roll Number";

                }

                if (columnName == "Division")

                {

                    if (string.IsNullOrEmpty(Division))

                        result = "Please select Division";

                }

                return result;

            }

        }

    }

.xaml code

     <Window.Resources>

        <Style TargetType="{x:Type TextBox}">

            <Setter Property="VerticalAlignment" Value="Center" />

            <Setter Property="Margin" Value="0,2,40,2" />

            <Setter Property="Validation.ErrorTemplate">

                <Setter.Value>

                    <ControlTemplate>

                        <DockPanel LastChildFill="True">

                            <Border Background="OrangeRed" DockPanel.Dock="right" Margin="5,0,0,0" 

                                Width="20" Height="20" CornerRadius="5"

                                ToolTip="{Binding ElementName=customAdorner, 

                                          Path=AdornedElement.(Validation.Errors)[0].ErrorContent}">

                                <TextBlock Text="?" VerticalAlignment="center" HorizontalAlignment="center" 

                                   FontWeight="Bold" Foreground="white" />

                            </Border>

                            <AdornedElementPlaceholder Name="customAdorner" VerticalAlignment="Center" >

                                <Border BorderBrush="red" BorderThickness="1" />

                            </AdornedElementPlaceholder>

                        </DockPanel>

                    </ControlTemplate>

                </Setter.Value>

            </Setter>

        </Style>

        <Style TargetType="{x:Type ComboBox}">

            <Setter Property="VerticalAlignment" Value="Center" />

            <Setter Property="Margin" Value="0,2,40,2" />

            <Setter Property="Validation.ErrorTemplate">

                <Setter.Value>

                    <ControlTemplate>

                        <DockPanel LastChildFill="True">

                            <Border Background="OrangeRed" DockPanel.Dock="right" Margin="5,0,0,0" 

                                Width="20" Height="20" CornerRadius="5"

                                ToolTip="{Binding ElementName=customAdorner, 

                                          Path=AdornedElement.(Validation.Errors)[0].ErrorContent}">

                                <TextBlock Text="!" VerticalAlignment="center" HorizontalAlignment="center" 

                                   FontWeight="Bold" Foreground="white" />

                            </Border>

                            <AdornedElementPlaceholder Name="customAdorner" VerticalAlignment="Center" >

                                <Border BorderBrush="red" BorderThickness="1" />

                            </AdornedElementPlaceholder>

                        </DockPanel>

                    </ControlTemplate>

                </Setter.Value>

            </Setter>

        </Style>

    </Window.Resources>

    <Grid x:Name="grdStudentData" Margin="0,20">

        <Grid.ColumnDefinitions>

            <ColumnDefinition Width="Auto" />

            <ColumnDefinition Width="*" />

        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>

            <RowDefinition Height="auto" />

            <RowDefinition Height="auto" />

            <RowDefinition Height="auto" />

            <RowDefinition Height="auto" />

        </Grid.RowDefinitions>

        <Grid.CommandBindings>

            <CommandBinding Command="New" CanExecute="Confirm_CanExecute" Executed="Confirm_Executed" />

        </Grid.CommandBindings>

        <Label Content="First Name:" Grid.Column="0" Grid.Row="0" />

        <Label Content="Division:" Grid.Column="0" Grid.Row="1" />

        <Label Content="Roll No:" Grid.Column="0" Grid.Row="2" />

        

        <TextBox x:Name="txtFirstName" Grid.Row="0" Grid.Column="1" 

             Validation.Error="Validation_Error"

             Text="{Binding UpdateSourceTrigger=PropertyChanged, Path=FirstName,

                    ValidatesOnDataErrors=true, NotifyOnValidationError=true}" />

        <ComboBox x:Name="cbpdepartment" Grid.Row="1" Grid.Column="1" ItemsSource="{Binding Divisions,Mode=TwoWay}" Validation.Error="Validation_Error" SelectedItem="{Binding UpdateSourceTrigger=PropertyChanged, Path=Division,ValidatesOnDataErrors=true, NotifyOnValidationError=true}" />

        <TextBox x:Name="txtRollNumber" Grid.Row="2" Grid.Column="1" 

             Validation.Error="Validation_Error"

             Text="{Binding UpdateSourceTrigger=PropertyChanged, Path=RollNumber,

                    ValidatesOnDataErrors=true, NotifyOnValidationError=true}" />

        

        <Button Content="Submit" Grid.ColumnSpan="2" Grid.Row="3" Grid.Column="1" Margin="0,0,10,0"

            HorizontalAlignment="right" VerticalAlignment="Center" Command="New"/>

    </Grid>

.xaml.cs code

      private int _errors = 0;

        private Student _student = new Student();

        public ValidationPart1()

        {

            InitializeComponent();

            _student.Divisions = new List<string>();

            _student.Divisions.Add(string.Empty);

            _student.Divisions.Add("Fifth");

            _student.Divisions.Add("Sixth");

            _student.Divisions.Add("Seventh");

            grdStudentData.DataContext = _student;

        }

        private void Confirm_CanExecute(object sender, CanExecuteRoutedEventArgs e)

        {

            e.CanExecute = _errors == 0;

            e.Handled = true;

        }

        private void Confirm_Executed(object sender, ExecutedRoutedEventArgs e)

        {

           //Insert logic of the page

        }

        private void Validation_Error(object sender, ValidationErrorEventArgs e)

        {

            if (e.Action == ValidationErrorEventAction.Added)

                _errors++;

            else

                _errors--;

        }

        

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