In this blog I will show you how can we apply validation in WPF as displayed in below screenshot:

validation

Step 1: Design a keying screen like the image being displayed below,

Design 1

Step 2: Add a class User.cs,

  1. namespace DotnetBullet.WPFValidationWay1
  2. {
  3. public class User
  4. {
  5. #region Variables
  6. string _userName = string.Empty;
  7. int _age;
  8. string _mobileNo = string.Empty;
  9. #endregion
  11. #region Properties
  12. /// <summary>
  13. /// Gets or sets the name of the user.
  14. /// </summary>
  15. /// <value>
  16. /// The name of the user.
  17. /// </value>
  18. public string UserName
  19. {
  20. get
  21. {
  22. return _userName;
  23. }
  24. set
  25. {
  26. _userName = value;
  27. }
  28. }
  30. /// <summary>
  31. /// Gets or sets the age.
  32. /// </summary>
  33. /// <value>
  34. /// The age.
  35. /// </value>
  36. public int Age
  37. {
  38. get
  39. {
  40. return _age;
  41. }
  42. set
  43. {
  44. _age = value;
  45. }
  46. }
  48. /// <summary>
  49. /// Gets or sets the mobile no.
  50. /// </summary>
  51. /// <value>
  52. /// The mobile no.
  53. /// </value>
  54. public string MobileNo
  55. {
  56. get
  57. {
  58. return _mobileNo;
  59. }
  60. set
  61. {
  62. _mobileNo = value;
  63. }
  64. }
  65. #endregion
  66. }
  67. }
Step 3: Add a class RequiredFiedValidationRule.cs for Required Field Validation,
  1. using System.Globalization;
  2. using System.Windows.Controls;
  4. namespace DotnetBullet.WPFValidationWay1
  5. {
  6. class RequiredFiedValidationRule : ValidationRule
  7. {
  8. public RequiredFiedValidationRule()
  9. {
  11. }
  12. public override ValidationResult Validate(object value, CultureInfo cultureInfo)
  13. {
  14. if (value.ToString().Length > 0)
  15. {
  16. return new ValidationResult(true, null);
  17. }
  18. else
  19. {
  20. return new ValidationResult(false, "Required Field Validation");
  21. }
  22. }
  23. }
  24. }
Step 4: Add Control Template like this:
  1. <ControlTemplate x:Key="validationTemplate">
  2. <DockPanel>
  3. <TextBlock Foreground="Red" FontSize="25" Text="*" DockPanel.Dock="Right">
  4. </TextBlock>
  5. <AdornedElementPlaceholder/>
  6. </DockPanel>
  7. </ControlTemplate>
Step 5: Add Style,
  1. <Style x:Key="InputControlErrors" TargetType="{x:Type TextBox}">
  2. <Style.Triggers>
  3. <Trigger Property="Validation.HasError" Value="true">
  4. <Setter Property="ToolTip"
  5. Value="{Binding RelativeSource={x:Static RelativeSource.Self},
  6. Path=(Validation.Errors)[0].ErrorContent}"/>
  7. </Trigger>
  8. </Style.Triggers>
  9. </Style>
Step 6: Modify textbox XAML,
  1. <TextBox HorizontalAlignment="Left" Height="23" Margin="159,14,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="258"
  2. Validation.ErrorTemplate="{StaticResource validationTemplate}" Style="{StaticResource InputControlErrors}"
  3. Name="txtName">
  4. <TextBox.Text>
  5. <Binding Path="UserName" Source="{StaticResource user}" UpdateSourceTrigger="PropertyChanged">
  6. <Binding.ValidationRules>
  7. <c:RequiredFiedValidationRule></c:RequiredFiedValidationRule>
  8. </Binding.ValidationRules>
  9. </Binding>
  10. </TextBox.Text>
  12. </TextBox>
Repeat the same for all the 3 controls.

The complete XAML code for UI is as follows:
  1. <Window x:Class="DotnetBullet.WPFValidationWay1.MainWindow"
  2. xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  3. xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  4. xmlns:c="clr-namespace:DotnetBullet.WPFValidationWay1"
  5. Title="DotNetBullet.com Binding Validation Way" Height="250" Width="450">
  7. <Window.Resources>
  8. <c:User x:Key="user"/>
  9. <ControlTemplate x:Key="validationTemplate">
  10. <DockPanel>
  11. <TextBlock Foreground="Red" FontSize="25" Text="*" DockPanel.Dock="Right"></TextBlock>
  12. <AdornedElementPlaceholder/>
  13. </DockPanel>
  14. </ControlTemplate>
  16. <Style x:Key="InputControlErrors" TargetType="{x:Type TextBox}">
  17. <Style.Triggers>
  18. <Trigger Property="Validation.HasError" Value="true">
  19. <Setter Property="ToolTip"
  20. Value="{Binding RelativeSource={x:Static RelativeSource.Self},
  21. Path=(Validation.Errors)[0].ErrorContent}"/>
  22. </Trigger>
  23. </Style.Triggers>
  24. </Style>
  25. </Window.Resources>
  27. <Grid Margin="0,0,0,5">
  28. <Label Content="Name" HorizontalAlignment="Left" Margin="42,10,0,0" VerticalAlignment="Top"/>
  29. <Label Content="Age" HorizontalAlignment="Left" Margin="42,67,0,0" VerticalAlignment="Top"/>
  30. <Label Content="Mobile no." HorizontalAlignment="Left" Margin="42,127,0,0" VerticalAlignment="Top"/>
  32. <TextBox HorizontalAlignment="Left" Height="23" Margin="159,14,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="258"
  33. Validation.ErrorTemplate="{StaticResource validationTemplate}" Style="{StaticResource InputControlErrors}"
  34. Name="txtName">
  35. <TextBox.Text>
  36. <Binding Path="UserName" Source="{StaticResource user}" UpdateSourceTrigger="PropertyChanged">
  37. <Binding.ValidationRules>
  38. <c:RequiredFiedValidationRule></c:RequiredFiedValidationRule>
  39. </Binding.ValidationRules>
  40. </Binding>
  41. </TextBox.Text>
  43. </TextBox>
  45. <TextBox HorizontalAlignment="Left" Height="23" Margin="159,70,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="258"
  46. Validation.ErrorTemplate="{StaticResource validationTemplate}" Style="{StaticResource InputControlErrors}"
  47. Name="txtAge">
  48. <TextBox.Text>
  49. <Binding Path="Age" Source="{StaticResource user}" UpdateSourceTrigger="PropertyChanged">
  50. <Binding.ValidationRules>
  51. <c:RequiredFiedValidationRule></c:RequiredFiedValidationRule>
  52. </Binding.ValidationRules>
  53. </Binding>
  54. </TextBox.Text>
  55. </TextBox>
  57. <TextBox HorizontalAlignment="Left" Height="23" Margin="159,130,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="258"
  58. Validation.ErrorTemplate="{StaticResource validationTemplate}" Style="{StaticResource InputControlErrors}"
  59. Name="txtMobileNo">
  60. <TextBox.Text>
  61. <Binding Path="MobileNo" Source="{StaticResource user}" UpdateSourceTrigger="PropertyChanged">
  62. <Binding.ValidationRules>
  63. <c:RequiredFiedValidationRule></c:RequiredFiedValidationRule>
  64. </Binding.ValidationRules>
  65. </Binding>
  66. </TextBox.Text>
  68. </TextBox>
  70. </Grid>
  71. </Window>
If you face any issue regarding this code please feel free to ask me.