如果您查看输出窗口，您应该会看到绑定异常.

if you look at your output window you should see the binding exception.

您遇到的问题如下:在您的用户控件中，您会将标签绑定到用户控件的 DP ProtocolNumber 而不是 DataContext，因此您必须将例如元素名称添加到绑定.

The problem you have is the following: within your usercontrol you will bind the label to the DP ProtocolNumber of your usercontrol and not the DataContext, so you have to add for example the element name to the binding.

<UserControl Name="MainOptionsPanel"
    x:Class="ExperienceMainControls.MainControls"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    x:Name="uc"
    >
<Label Height="Auto" Name="numberLabel">Protocol:</Label>
<Label Content="{Binding Path=ProtocolNumber, ElementName=uc}" Name="protocolNumberLabel"/>
(...)
</UserControl>

为了解决一些问题，如果您更改 MainWindow 中的绑定，您的用户控件也可以工作.但是你必须使用RelativeSource绑定到MainWindow的DataContext.

to clear some things up, your usercontrol also works if you change the binding in your MainWindow. but you have to bind to the DataContext of the MainWindow with RelativeSource.

    <expControl:MainControls ProtocolNumber="{Binding Path=Number, RelativeSource={RelativeSource AncestorType={x:Type Window}}}" />