Как реализовать WPF как MVVM с использованием сетки данных

Question

1. папка "Views"

MainWindow.xaml

<Window x:Class="_20200203_mvvm_gyudong.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:_20200203_mvvm_gyudong"
        mc:Ignorable="d"
        Title="MVVM in WPF - Gyudong Kim" Height="450" Width="800">
    <Border Padding="10">
        <Grid Name ="Grid" HorizontalAlignment="Left" Height="400" VerticalAlignment="Center" Width="770">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="6*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>
            <Button Name="BtnRead" Content="Read" Grid.Row="0" Grid.Column="1" Margin="0 10 0 10" Click="BtnRead_Click"/>
            <Button Name="BtnInsert" Content="Insert" Grid.Row="1" Grid.Column="1" Margin="0 10 0 10" Click="BtnInsert_Click"/>
            <Button Name="BtnUpdate" Content="Update" Grid.Row="2" Grid.Column="1" Margin="0 10 0 10" Click="BtnUpdate_Click"/>
            <Button Name="BtnDelete" Content="Delete" Grid.Row="3" Grid.Column="1" Margin="0 10 0 10" Click="BtnDelete_Click"/>
            <DataGrid Name="datagridStudent" Grid.RowSpan="4" Width="640" Height="390" Margin="0 10 0 10"
                      AutoGenerateColumns="False" CanUserResizeRows="False" ItemsSource="{Binding Path=tblStudent}">
                <DataGrid.Columns>
                    <DataGridTextColumn Header="grade" Binding="{Binding Path=grade}" Width="120"/>
                    <DataGridTextColumn Header="cclass" Binding="{Binding Path=cclass}" Width="120"/>
                    <DataGridTextColumn Header="no" Binding="{Binding Path=no}" Width="150"/>
                    <DataGridTextColumn Header="name" Binding="{Binding Path=name}" Width="120"/>
                    <DataGridTextColumn Header="score" Binding="{Binding Path=score}" Width="120"/>
                </DataGrid.Columns>
            </DataGrid>
        </Grid>
    </Border>
</Window>

MainWindow.xaml.cs

using System;
using System.Windows;
using System.Windows.Controls;
using _20200203_mvvm_gyudong.ViewModels;

namespace _20200203_mvvm_gyudong
{
    public partial class MainWindow : Window
    {
        StudentViewModel st = new StudentViewModel();
        public MainWindow()
        {
            InitializeComponent();
        }

        private void BtnRead_Click(object sender, RoutedEventArgs e)
        {
            st.SelectView();
        }

        private void BtnInsert_Click(object sender, RoutedEventArgs e)
        {
            string insertQuery = "INSERT INTO student VALUES (@grade, @cclass, @no, @name, @score)";
            st.ExecuteQuery(insertQuery);
        }

        private void BtnUpdate_Click(object sender, RoutedEventArgs e)
        {
            string updateQuery = "UPDATE student SET grade = @grade, cclass = @cclass, no = @no, name = @name, score = @score WHERE grade = @grade";
            st.ExecuteQuery(updateQuery);
        }

        private void BtnDelete_Click(object sender, RoutedEventArgs e)
        {
            string deleteQuery = "DELETE FROM student WHERE grade = @grade";
            st.ExecuteQuery(deleteQuery);
        }
    }
}

папка "Модели"

Student.cs

namespace _20200203_mvvm_gyudong.Models
{
    public class Student
    {
        public int grade { get; set; }
        public int cclass { get; set; }
        public int no { get; set; }
        public string name { get; set; }
        public string score { get; set; }
    }
}

папка "ViewModels"

StudentViewModel.cs

using System;
using MySql.Data;
using MySql.Data.MySqlClient;
using System.Data;
using System.Windows;
using _20200203_mvvm_gyudong.Models;
using _20200203_mvvm_gyudong.Properties;

namespace _20200203_mvvm_gyudong.ViewModels
{
    public class StudentViewModel
    {
        MySqlConnection conn = new MySqlConnection("Server=localhost;userid=root;password=111111;Database=ACK");
        MySqlCommand cmd;
        MySqlDataAdapter adapter;
        DataSet ds;
        Student std = new Student();

        public void OpenConn()
        {
            if (conn.State == ConnectionState.Closed) { conn.Open(); }
        }
        public void CloseConn()
        {
            if (conn.State == ConnectionState.Open) { conn.Close(); }
        }
        public void SelectView()
        {
            try
            {
                conn.Open();
                cmd = new MySqlCommand("Select * from student", conn);
                adapter = new MySqlDataAdapter(cmd);
                ds = new DataSet();
                adapter.Fill(ds, "tblStudent");
                datagridStudent.DataContext = ds; // How to bind datagrid..?
            }
            catch (MySqlException ex)
            {
                MessageBox.Show(ex.ToString());
            }
            finally
            {
                conn.Close();
            }
        }

        public void ExecuteQuery(string query)
        {
            try
            {
                OpenConn();
                cmd = new MySqlCommand(query, conn);
                cmd.Parameters.Add("@grade", MySqlDbType.Int32).Value = std.grade; // x
                cmd.Parameters.Add("@cclass", MySqlDbType.Int32).Value = std.cclass; // x
                cmd.Parameters.Add("@no", MySqlDbType.Int64).Value = std.no; // x
                cmd.Parameters.Add("@name", MySqlDbType.VarChar, 100).Value = std.name; // x
                cmd.Parameters.Add("@score", MySqlDbType.VarChar, 20).Value = std.score; // x
                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                CloseConn();
            }
        }
    }
}

---

Это мой второй вопрос.

I хотите, чтобы CRUD-сетка данных в приложении WPF была реализована в виде MVVM.

Как исправить код?

(Честно говоря, я не очень хорошо понимаю шаблон MVVM.)

Спасибо за вашу доброту.