你好 Wangminwei，
WPF对于错误的提示有一个默认控件 Validation Class，你可以查看 Validation.Errors 和 Validation.ErrorTemplate ，它会在出错误的时候给你提示，一个红框，并且显示错误信息。具体的做法你可以参看完MSDN文档以后看CodeProject上的这个例子：http://www.codeproject.com/Articles/15239/Validation-in-Windows-Presentation-Foundation
但是这个跟你的要求不符合，如果你想要这种对话框的话，你可能需要自己写自定义控件，比如这里我做了一个透明的窗体并且带了线和显示文字的label：
<Window x:Class="WpfApplication1.CustomWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="CustomWindow" Height="285.882" Width="421.176" AllowsTransparency="True" WindowStyle="None" Background="#00FFFFFF">
<Grid>
<Canvas HorizontalAlignment="Left" Height="100" Margin="30,139,0,0" VerticalAlignment="Top" Width="142">
<Line
X1="0" Y1="70"
X2="130" Y2="0"
Stroke="Black"
StrokeThickness="4" Height="90" Width="132" />
</Canvas>
<Label Content="Label" HorizontalAlignment="Left" Margin="189,108,0,0" VerticalAlignment="Top" Width="199" Height="57"/>
</Grid>
</Window>
Barry
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