c# – 如何在WPF应用程序中显示错误消息？

概述我正在尝试使用 WPF创建一个应用程序.我正在尝试使用MVVM模型完全构建它.但是,我很困惑如何正确显示错误消息.我认为这将是微不足道的一步,但似乎是最复杂的. 我使用xaml创建了以下视图 <StackPanel Style="{StaticResource Col}"> <DockPanel> <Grid DockPanel.Dock="Top"> 我正在尝试使用 @L_502_0@创建一个应用程序.我正在尝试使用MVVM模型完全构建它.但是,我很困惑如何正确显示错误消息.我认为这将是微不足道的一步,但似乎是最复杂的.

我使用xaml创建了以下视图

<StackPanel Style="{StaticResource Col}">    <DockPanel>        <GrID DockPanel.Dock="top">            <GrID.ColumnDeFinitions >                <ColumnDeFinition WIDth="*" ></ColumnDeFinition>                <ColumnDeFinition WIDth="*"></ColumnDeFinition>            </GrID.ColumnDeFinitions>            <StackPanel GrID.Column="0" Style="{StaticResource Col}">                <Label Content="name" Style="{StaticResource Formlabel}" />                <border Style="{StaticResource Forminputborder}">                    <TextBox x:name="name" Style="{StaticResource FormControl}" Text="{Binding name,ValIDatesOnDataErrors=True,NotifyOnValIDationError=True,UpdateSourceTrigger=PropertyChanged}" />                </border>            </StackPanel>            <StackPanel GrID.Column="1" Style="{StaticResource Col}">                <Label Content="Phone Number" Style="{StaticResource Formlabel}" />                <border Style="{StaticResource Forminputborder}">                    <TextBox x:name="Phone" Style="{StaticResource FormControl}" Text="{Binding Phone,UpdateSourceTrigger=PropertyChanged}" />                </border>            </StackPanel>        </GrID>        <StackPanel OrIEntation="Horizontal" HorizontalAlignment="Center">            <button Style="{StaticResource Primarybutton}" Command="{Binding Create}">Create</button>            <button>reset</button>        </StackPanel>    </DockPanel></StackPanel>

然后我创建了以下viewmodel

public class vendorviewmodel : viewmodel{    protected Readonly IUnitOfWork UnitOfWork;    private string _name { get; set; }    private string _Phone { get; set; }    public vendorviewmodel()        : this(new UnitOfWork())    {    }    public vendorviewmodel(IUnitOfWork unitOfWork)    {        UnitOfWork = unitOfWork;    }    [required(ErrorMessage = "The name is required")]    [MinLength(5,ErrorMessage = "name must be more than or equal to 5 letters")]     [MaxLength(50,ErrorMessage = "name must be less than or equal to 50 letters")]     public string name    {        get { return _name; }        set        {            _name = value;            NotifyPropertyChanged();        }    }    public string Phone    {        get { return _Phone; }        set        {            _Phone = value;            NotifyPropertyChanged();        }    }    /// <summary>    /// Gets the collection of customer loaded from the data store.    /// </summary>    public ICollection<vendor> vendors { get; private set; }    protected voID Addvendor()    {        var vendor = new vendor(name,Phone);        UnitOfWork.vendors.Add(vendor);    }    public ICommand Create    {        get        {            return new ActionCommand(p => Addvendor(),p => IsValIDRequest());        }    }    public bool IsValIDRequest()    {        // There got to be a better way to check if everything passed or Now...        return IsValID("name") && IsValID("Phone");    }}

这是我的viewmodel基类的样子

public abstract class viewmodel : ObservableObject,IDataErrorInfo{    /// <summary>    /// Gets the valIDation error for a property whose name matches the specifIEd <see cref="columnname"/>.    /// </summary>    /// <param name="columnname">The name of the property to valIDate.</param>    /// <returns>Returns a valIDation error if there is one,otherwise returns null.</returns>    public string this[string columnname]    {        get { return OnValIDate(columnname); }    }    /// <summary>    /// ValIDates a property whose name matches the specifIEd <see cref="propertyname"/>.    /// </summary>    /// <param name="propertyname">The name of the property to valIDate.</param>    /// <returns>Returns a valIDation error,if any,otherwise returns null.</returns>    protected virtual string OnValIDate(string propertyname)    {        var context = new ValIDationContext(this)        {            Membername = propertyname        };        var results = new Collection<ValIDationResult>();        bool isValID = ValIDator.TryValIDateObject(this,context,results,true);        if (!isValID)        {            ValIDationResult result = results.SingleOrDefault(p =>                                                                  p.Membernames.Any(membername => membername == propertyname));            if (result != null)                return result.ErrorMessage;        }        return null;    }    protected virtual bool IsValID(string propertyname)    {        return OnValIDate(propertyname) == null;    }    /// <summary>    /// Not supported.    /// </summary>    [Obsolete]    public string Error    {        get        {            throw new NotSupportedException();        }    }}

这是我的ObservableObject类

public class ObservableObject : INotifyPropertyChanged{    /// <summary>    /// Raised when the value of a property has changed.    /// </summary>    public event PropertyChangedEventHandler PropertyChanged;    /// <summary>    /// Raises <see cref="PropertyChanged"/> for the property whose name matches <see cref="propertyname"/>.    /// </summary>    /// <param name="propertyname">Optional. The name of the property whose value has changed.</param>    protected voID NotifyPropertyChanged([CallerMembername] string propertyname = "")    {        PropertyChangedEventHandler handler = PropertyChanged;        if (handler != null)        {            handler(this,new PropertyChangedEventArgs(propertyname));        }    }}

我的目标是在不正确的字段周围显示一个红色边框,然后在它下面显示错误消息,告诉使用出了什么问题.

如何正确显示错误？另外,如何在首次加载视图时不显示任何错误？

基于此blog,我需要编辑ValIDation.ErrorTemplate

所以我尝试将以下代码添加到App.xaml文件中

<!-- Style the error valIDation by showing the text message under the fIEld -->    <Style targettype="TextBox">        <Setter Property="ValIDation.ErrorTemplate">            <Setter.Value>                <ControlTemplate>                    <StackPanel>                        <border borderThickness="1" borderBrush="DarkRed">                            <StackPanel>                                <AdornedElementPlaceholder x:name="errorControl" />                            </StackPanel>                        </border>                        <TextBlock Text="{Binding AdornedElement.tooltip,Elementname=errorControl}" Foreground="Red" />                    </StackPanel>                </ControlTemplate>            </Setter.Value>        </Setter>        <Style.Triggers>            <Trigger Property="ValIDation.HasError" Value="true">                <Setter Property="borderBrush" Value="Red" />                <Setter Property="borderThickness" Value="1" />                <Setter Property="tooltip" Value="{Binding relativeSource={relativeSource Self},Path=(ValIDation.Errors)[0].ErrorContent}" />            </Trigger>        </Style.Triggers>    </Style>

但是这没有显示错误消息,也是在第一次加载视图时我得到一个错误.最后,即使表单生效, *** 作按钮也会保持禁用状态.

更新
将Property =“ValIDation.ErrorTemplate”移动到FormControl组后,它工作了.但是,错误消息似乎是通过按钮而不是按下按钮.此外,文本似乎没有垂直包装,允许边框覆盖其他控件,如下面的屏幕显示所示.

解决方法 我会尽力回答你的所有问题：

如何正确显示错误？

不应用ErrorTemplate,因为TextBox上的FormControl样式优先于包含ValIDation.ErrorTemplate的样式.将ValIDation.ErrorTemplate代码移动到FormControl样式将解决此问题.

另外,如何在首次加载视图时不显示任何错误？

如果不立即应用,必要验证的用途是什么？只有在开始键入字段时才会执行MinLength和MaxLength验证.

但是,错误消息似乎是通过按钮而不是按下按钮.

正如Will指出的那样,这是因为错误消息显示在AdornerLayer上,它不会干扰控件所在的层.您有以下选择：

>使用AdornerLayer但在控件之间留出一些空间
>使用工具提示显示错误消息
>在TextBox的模板中使用额外的TextBlock,以显示错误消息.

这些选项描述为here

总结

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