使用Web浏览器控件构建WPF项目时出错

Question

In my application, I have a UserControl in which I use a WebBrowser control.

The following is the code for the UserControl :

<UserControl x:Class="tool.ucMain"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="354" d:DesignWidth="440">
<Grid>
    <DockPanel>
        <WebBrowser Name="wbMap" DockPanel.Dock="Left" MinWidth="300"></WebBrowser>
        <DataGrid Name="grdSignals" DockPanel.Dock="Right" ItemsSource="{Binding}" AutoGenerateColumns="False">
        </DataGrid>
    </DockPanel>
</Grid>

I am using this UserControl in another UserControl which has a TabControl . This is the code for the other UserControl :

<Grid>
    <TabControl>
        <TabItem Name="tabMain" Header="Main">
            <uc:ucMain />
        </TabItem>
        <TabItem Name="tabDataExplorer" Header="Data Explorer"/>
    </TabControl>
</Grid>

The ucMain is the first UserControl . When I clean the project I can see the first user control. But when I build/run it, it disappears and I get the error as shown in the following image. I get this error even in design view.

Answer 1

I duplicated this behavior by creating a UserControl that contains the WebBrowser, and called that BrowserContainer. Then, I created another UserControl called BrowserBrowserContainer and added my first UserControl to that. After that, I added the BrowserBrowserContainer UserControl to my MainWindow.xaml file for my test project.

When I give the WebBrowser a name, such as "Browser", and then add the following code to the constructor for BrowserContainer, I get the exact same behavior that you describe.

public BrowserContainer()
{
    InitializeComponent();
    Browser.Source = new Uri("c:\\thisfiledoesntexist");
}

Naturally, the solution is not to set the Source, or to set it to something that is valid at design time. The parameterless constructor is called whether you're in design mode or not.

Answer 2

If you try to navigate to your local file you should always append file:/// in the front of your Uri path.

EDIT

I just tested it, I can see this error occurred in designer view of the Main Window. I can see Visual Studio tried to trigger the Loaded Event of the UserControl. Somehow the AppDomain.CurrentDomain.BaseDirectory returns the Visual Studio path.

The best way to skip this error might be using DesignerProperties.GetIsInDesignMode()

For example you can do the following to skip this error in designer view.

   private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        if (DesignerProperties.GetIsInDesignMode(this)) return;
        String appdir = System.IO.Path.GetDirectoryName(AppDomain.CurrentDomain.BaseDirectory);
        String mapPath = System.IO.Path.Combine(appdir, "MAP.html");
        ResultWebBrowser.Navigate(new Uri("file:///" + mapPath));
    }