关于#c##的问题：用toolkit.mvvm框架更新datagrid，在[RelayCommand]中绑定的代码中可以更新datagrid，同样的代码放到代码块中调用就无法更新datagrid

Question

用toolkit.mvvm框架更新datagrid，在[RelayCommand]中绑定的代码中可以更新datagrid，同样的代码放到代码块中调用就无法更新datagrid。
（使用vs2022community编程）

使用这段代码可以更新

[RelayCommand]
        private void AddNew()
        {
            Employees.Add(new Employee { CardId = "138", OrganizationName = "Raj" });//可以对datagrid进行更新
            //LoadExcelToList2();//这个不能更新datagrid不知道为什么，代码一样啊
        }

使用这段代码无法更新，不知道为什么

[RelayCommand]
        private void AddNew()
      {
            LoadExcelToList2();//这个不能更新datagrid不知道为什么，代码一样啊
        }
        public static void LoadExcelToList2()
        {
            var MyVM = new ViewModel();
            MyVM.Employees.Add(new Employee { CardId = "168", OrganizationName = "Raj"}); 
        }

完整代码如下：

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System.ComponentModel;
using System.Windows;

namespace WpfToolkitTest
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            //DataContext = new ViewModel();
        }
    }

    public partial class ViewModel : ObservableObject
    {
        public BindingList<Employee> Employees { get; set; }

        public ViewModel()
        {
            Employees = new BindingList<Employee>();
        }

        [RelayCommand]
        private void AddNew()
        {
            Employees.Add(new Employee { CardId = "138", OrganizationName = "Raj" });//可以对datagrid进行更新
            //LoadExcelToList2();//这个不能更新datagrid不知道为什么，代码一样啊
        }
        public static void LoadExcelToList2()
        {
            var MyVM = new ViewModel();
            MyVM.Employees.Add(new Employee { CardId = "168", OrganizationName = "Raj"}); 
        }
    }
}

using CommunityToolkit.Mvvm.ComponentModel;

namespace WpfToolkitTest
{
    public partial class Employee : ObservableObject
    {
        public string OrganizationName { get; set; }

        [ObservableProperty]
        private string cardId;//读卡器读取的卡号
    }
}

<Window x:Class="WpfToolkitTest.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:WpfToolkitTest"
        xmlns:hc="https://handyorg.github.io/handycontrol"
        Title="{Binding Title}"
        Width="900"
        Height="600"
        WindowStartupLocation="CenterScreen"
        mc:Ignorable="d" >
    <Window.DataContext>
        <local:ViewModel/>
    </Window.DataContext>
    <DockPanel Margin="5">
        <hc:UniformSpacingPanel Margin="0,5,0,0"
                       Spacing="10"
                       DockPanel.Dock="Bottom"
                       Orientation="Horizontal">
            <Button Content="Add New" Command="{Binding AddNewCommand}"/>
        </hc:UniformSpacingPanel>
        <DataGrid Name="dataGrid"
                  d:ItemsSource="{d:SampleData ItemCount=10}"
                  ItemsSource="{Binding Employees}"
                  CanUserAddRows="False"
                  AutoGenerateColumns="False">
            <DataGrid.Columns>
                <DataGridTextColumn Header="卡号" Binding="{Binding CardId}"/>
                <DataGridTextColumn Header="机构名称" Binding="{Binding OrganizationName}"/>
            </DataGrid.Columns>
        </DataGrid>
    </DockPanel>
</Window>

Answer 1

var MyVM = new ViewModel();
这里创建了新的模型，不是原来的那个