有什么办法可以在世界粮食论坛实现这一目标？
不，恐怕不行。
该错误消息是正确的，因为只有根元素（如for example a window）可以指定x:TypeArguments属性。
为了能够在XAML中示例化和使用泛型CustomKeyValuePair<K, V>类型，您必须为类型参数的每个组合创建它的非泛型子类，例如：

public class StringIntCustomKeyValuePair : CustomKeyValuePair<string, int> { }

• • XAML格式：**

<local:StringIntCustomKeyValuePair />

（译文）
如果您愿意牺牲一些性能，请尝试反思。
XAML：

<Window x:Class="GenericXamlMvce.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:GenericXamlMvce"
        xmlns:s="clr-namespace:System;assembly=netstandard"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>

        <TextBlock Grid.Column="0"
                               Grid.Row="0"
                               Text="Image: "
                               VerticalAlignment="Center"
                               Margin="5 0 2 0" />

        <ComboBox x:Name="DemoSelector"
                  Grid.Column="1"
                  Grid.Row="0"
                  SelectedIndex="0"
                  Margin="0 5 5 5"
                  DisplayMemberPath="Key"
                  SelectedValuePath="Value">
            <ComboBoxItem>
                <local:CustomKeyValuePair K="{x:Type s:String}" 
                                          V="{x:Type s:String}" 
                                          Key="Label To Show 01"
                                          Value="Content To Show 01" />
            </ComboBoxItem>

            <ComboBoxItem>
                <local:CustomKeyValuePair K="{x:Type s:String}" 
                                          V="{x:Type s:String}" 
                                          Key="Label To Show 02"
                                          Value="Content To Show 02" />
            </ComboBoxItem>
        </ComboBox>

        <TextBlock Grid.Column="0"
                   Grid.Row="1"
                   Grid.ColumnSpan="2"
                   Margin="10"
                   FontSize="20"
                   FontWeight="Bold"
                   Text="{Binding ElementName=DemoSelector, Path=SelectedValue}" />
    </Grid>
</Window>

C编号：

public record CustomKeyValuePair
{
    public CustomKeyValuePair()
    {
        KeyValuePair = Create(K, V, Key, Value);
    }

    public object Key { get; init; }
    public object Value { get; init; }

    public Type K { get; init; }
    public Type V { get; init; }

    public object KeyValuePair { get; init; }

    public static object Create(Type t, Type v, object key, object value)
    {
        if (t == null || v == null)
        {
            return null;
        }
        var type = typeof(CustomKeyValuePair<,>).MakeGenericType(t, v);
        var cctor = type.GetConstructor(new Type[] { t, v });
        return cctor.Invoke(new object[] { key, value });
    }
    
    public CustomKeyValuePair<K, V> Convert<K, V>()
    {
        return (CustomKeyValuePair<K, V>)KeyValuePair;
    }
}

public record CustomKeyValuePair<K, V>
{
    public CustomKeyValuePair() { }

    public CustomKeyValuePair(K key, V value)
    {
        Key = key;
        Value = value;
    }

    public K Key { get; init; }

    public V Value { get; init; }

    public void Deconstruct(out K key, out V value)
    {
        key = Key;
        value = Value;
    }
}