<Window x:Class="ErrorTest.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"

        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

        xmlns:local="clr-namespace:ErrorTest"

        mc:Ignorable="d"

        Title="MainWindow" Height="450" Width="800">

    <Grid>

        <TextBox HorizontalAlignment="Left"  

                 Height="50"   VerticalAlignment="Top" Width="237">

            <TextBox.Text>

                <Binding Path="FName"  NotifyOnValidationError="True"   

                    UpdateSourceTrigger="PropertyChanged">

                    <Binding.ValidationRules>

                        <local:ValidClass></local:ValidClass>

                    </Binding.ValidationRules>

                </Binding>

            </TextBox.Text>

        </TextBox>



    </Grid>

</Window>

添加一个验证文件

  public class ValidClass : ValidationRule

    {

        public override ValidationResult Validate(object value, CultureInfo cultureInfo)

        {

            var a = value.ToString();

            if (string.IsNullOrWhiteSpace(a))

            {

                return new ValidationResult(false, "不可为空");

            }

            else

            {

                return new ValidationResult(true, null);

            }

        }

    }

添加一个ViewModel

    public class VM : INotifyPropertyChanged

    {

 

        private string _FName;



        public string FName

        {

            get { return _FName; }

            set { _FName = value; RaisePropertyChanged("FName"); }

        }

 

        private void RaisePropertyChanged(string name)

        {

            if (PropertyChanged != null)

                PropertyChanged(this,new PropertyChangedEventArgs (name));

        }

        public event PropertyChangedEventHandler PropertyChanged;

    }