Csharp Xamarin中出错.表单：应用程序的分部声明不能指定不同的基类

我在我的Xamarin.Forms项目中遇到了一个问题，我正在寻求帮助解决它.我遇到以下错误:

Severity Code Description Project File Line Suppression State Error CS0263 Partial declarations of 'App' must not specify different base classes BeautyFly C:\Users\lenovo\Desktop\BeautyFly\BeautyFly\BeautyFly\App.xaml.cs 9 Active

此外，还有一个相关的错误:

Severity Code Description Project File Line Suppression State Error CS0103 The name 'MainPage' does not exist in the current context BeautyFly C:\Users\lenovo\Desktop\BeautyFly\BeautyFly\BeautyFly\App.xaml.cs 19 Active

Context:个

项目 struct :

名为"BeautyFly"的Xamarin.Forms项目

App.xaml.cs文件包含App类定义

应用程序主页的MainPage.xaml和MainPage.xaml.cs文件

代码片段:

App.xaml:

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="BeautyFly.App">

    <StackLayout>
        <Entry x:Name="resultEntry" Text="0" HorizontalOptions="FillAndExpand" VerticalOptions="EndAndExpand" FontSize="30" HorizontalTextAlignment="End"/>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="*" />
                <RowDefinition Height="*" />
                <RowDefinition Height="*" />
                <RowDefinition Height="*" />
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>

            <Button Text="7" Clicked="OnNumberClicked" Grid.Row="1" Grid.Column="0" />
            <Button Text="8" Clicked="OnNumberClicked" Grid.Row="1" Grid.Column="1" />
            <Button Text="9" Clicked="OnNumberClicked" Grid.Row="1" Grid.Column="2" />
            <Button Text="/" Clicked="OnOperatorClicked" Grid.Row="1" Grid.Column="3" />

            <Button Text="4" Clicked="OnNumberClicked" Grid.Row="2" Grid.Column="0" />
            <Button Text="5" Clicked="OnNumberClicked" Grid.Row="2" Grid.Column="1" />
            <Button Text="6" Clicked="OnNumberClicked" Grid.Row="2" Grid.Column="2" />
            <Button Text="*" Clicked="OnOperatorClicked" Grid.Row="2" Grid.Column="3" />

            <Button Text="1" Clicked="OnNumberClicked" Grid.Row="3" Grid.Column="0" />
            <Button Text="2" Clicked="OnNumberClicked" Grid.Row="3" Grid.Column="1" />
            <Button Text="3" Clicked="OnNumberClicked" Grid.Row="3" Grid.Column="2" />
            <Button Text="-" Clicked="OnOperatorClicked" Grid.Row="3" Grid.Column="3" />

            <Button Text="0" Clicked="OnNumberClicked" Grid.Row="4" Grid.Column="0" />
            <Button Text="." Clicked="OnDecimalClicked" Grid.Row="4" Grid.Column="1" />
            <Button Text="=" Clicked="OnEqualClicked" Grid.Row="4" Grid.Column="2" />
            <Button Text="+" Clicked="OnOperatorClicked" Grid.Row="4" Grid.Column="3" />
        </Grid>
    </StackLayout>

</ContentPage>

App.xaml.cs:

using BeautyFly.Services;
using BeautyFly.Views;
using System;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

namespace BeautyFly
{
    public partial class App : Application
    {
        private string currentInput = string.Empty;
        private string currentOperator = string.Empty;
        private double result = 0;
        public App()
        {
            InitializeComponent();

            DependencyService.Register<MockDataStore>();
            MainPage = new AppShell();
        }
        private void OnNumberClicked(object sender, EventArgs e)
        {
            Button button = (Button)sender;
            currentInput += button.Text;
            resultEntry.Text = currentInput;
        }

        private void OnOperatorClicked(object sender, EventArgs e)
        {
            Button button = (Button)sender;
            currentOperator = button.Text;
            result = double.Parse(currentInput);
            currentInput = string.Empty;
        }

        private void OnEqualClicked(object sender, EventArgs e)
        {
            double secondOperand = double.Parse(currentInput);

            switch (currentOperator)
            {
                case "+":
                    result += secondOperand;
                    break;
                case "-":
                    result -= secondOperand;
                    break;
                case "*":
                    result *= secondOperand;
                    break;
                case "/":
                    if (secondOperand != 0)
                        result /= secondOperand;
                    else
                        resultEntry.Text = "Error";
                    break;
            }

            resultEntry.Text = result.ToString();
            currentInput = string.Empty;
        }

        private void OnDecimalClicked(object sender, EventArgs e)
        {
            if (!currentInput.Contains("."))
            {
                currentInput += ".";
                resultEntry.Text = currentInput;
            }
        }
    }
}

采取的故障排除步骤:

已判断App类的继承 已验证MainPage类及其引用

Questions:个

是什么原因导致我的App.xaml.cs文件中出现"‘App’的部分声明不能指定不同的基类"错误？

如何解决"当前上下文中不存在主页面名称"的错误？

我的代码中是否有需要判断的特定区域来确定和解决此问题？

如有任何指导或建议，我们将不胜感激.谢谢!