窗口加载的事件处理程序：“确保事件失败”

Question

I'm trying to do the simple task of adding an event handler for the window loading. I'm using visual studio 2017. When I type Loaded="" and use IntelliSense to add a new event handler, I get the error message "Ensure Event Failed" and no other information. What is wrong?

XAML:

<Window x:Class="MLD_UI_1.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:MLD_UI_1"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" MinHeight="700" Width="525" MinWidth="1050"
    Loaded="">
    <Grid Background="{StaticResource MainBackgroundBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="10"/>
            <RowDefinition Height="40"/>
            <RowDefinition Height="*" MinHeight="80"/>
            <RowDefinition Height="200"/>
            <RowDefinition Height="10"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="10"/>
            <ColumnDefinition Width="*" MinWidth="100"/>
            <ColumnDefinition Width="*" MinWidth="100"/>
            <ColumnDefinition Width="10"/>
        </Grid.ColumnDefinitions>
        <Border BorderThickness="2 2 1 2" BorderBrush="Black" Grid.Column="1" Grid.Row="1" Background="{StaticResource UvGradientBrush}" CornerRadius="5 0 0 5"/>
        <Border BorderThickness="1 2 2 2" BorderBrush="Black" Grid.Column="2" Grid.Row="1" Background="{StaticResource IrGradientBrush}" CornerRadius="0 5 5 0"/>
        <Border BorderThickness="2 2 1 2" BorderBrush="Black" Grid.Column="1" Grid.Row="3" Background="{StaticResource GradientBrush}" CornerRadius="5 0 0 5"/>
        <Border BorderThickness="1 2 2 2" BorderBrush="Black" Grid.Column="2" Grid.Row="3" Background="{StaticResource GradientBrush}" CornerRadius="0 5 5 0"/>
        <StackPanel Grid.Column="1" Grid.Row="1" Orientation="Horizontal" Margin="10 0 10 0">
            <TextBlock Text="UV" FontFamily="Tahoma" Foreground="White" VerticalAlignment="Center" FontSize="20"/>
        </StackPanel>
        <StackPanel Grid.Column="2" Grid.Row="1" Orientation="Horizontal" Margin="10 0 10 0">
            <TextBlock Text="IR" FontFamily="Tahoma" Foreground="White" VerticalAlignment="Center" FontSize="20"/>
        </StackPanel>
        <Image x:Name="imagePane1" Grid.Column="1" HorizontalAlignment="Stretch" Grid.Row="2" VerticalAlignment="Stretch" Margin="2 2 2 2"/>
        <Image x:Name="imagePane2" Grid.Column="2" HorizontalAlignment="Stretch" Grid.Row="2" VerticalAlignment="Stretch" Margin="2 2 2 2"/>
    </Grid>
</Window>

Answer 1

The namespace in x:Class was incorrect; it did not match the namespace in my code behind:

Changing x:Class="MLD_UI_1.MainWindow" to x:Class="MLD_UI_2.MainWindow" fixed everything.