BindingExpression 路径错误：'SystemParameters'

Question

While updating my software, I started facing this BindingExpression error.

System.Windows.Data Error: 40: BindingExpression path error: 'SystemParameters' property not found on 'object' ''MainViewModel' (HashCode=4781813)'. BindingExpression:Path=SystemParameters.PrimaryScreenHeight; DataItem='MainViewModel' (HashCode=4781813); target element is 'MainWindow' (Name='XXX'); target property is 'Height' (type 'Double')

System.Windows.Data Error: 40: BindingExpression path error: 'SystemParameters' property not found on 'object' ''MainViewModel' (HashCode=4781813)'. BindingExpression:Path=SystemParameters.PrimaryScreenWidth; DataItem='MainViewModel' (HashCode=4781813); target element is 'MainWindow' (Name='XXX'); target property is 'Width' (type 'Double')*

Reading the above error, it seems that it couldn't find the SystemParameters object in MainViewModel .

<Window x:Name="XXXX" x:Class="XXXX.Views.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:XXXX"
    xmlns:localize="http://gu.se/Localization"
    xmlns:properties="clr-namespace:XXXX.Properties"
    mc:Ignorable="d"
    d:DesignHeight="1080" d:DesignWidth="1920"
    Title=""
    WindowStyle="None"
    ResizeMode="NoResize"
    WindowStartupLocation="CenterScreen" WindowState="{Binding WindowState, Mode=TwoWay}"
    DataContext="{Binding Main, Source ={StaticResource Locator}}"
    Height="{Binding SystemParameters.PrimaryScreenHeight}" 
    Width="{Binding SystemParameters.PrimaryScreenWidth}" Background="#FFCCCCCC">

   <Window.Resources>

When I start my application, the Initializer.cs class is called which initializes all the parameters and creates an instance of MainWindow . By debugging, I discovered that the issue seems to appear when I call the method window.Show() and then my application crashes instantly.

MainWindow window = new MainWindow();
window.Show();

Answer 1

A Binding will resolve the property path using the DataContext of an element by default (which is inherited). The PrimaryScreenHeight and PrimaryScreenWidth properties are static and part of the type SystemParameters , which is a static type, that is not part of the data context. To solve the issue you can:

• Use the x:Static markup extension to refer to static properties.

  Implements a markup extension that returns static field and property references .

   Height="{x:Static SystemParameters.PrimaryScreenHeight}" Width="{x:Static SystemParameters.PrimaryScreenWidth}"

• If you need to apply a value converter, you can use the x:Static markup extension for the Source .

   Height="{Binding Source={x:Static SystemParameters.PrimaryScreenHeight}, Converter={StaticResource MyConverter}}" Width="{Binding Source={x:Static SystemParameters.PrimaryScreenWidth}, Converter={StaticResource MyConverter}}"