如何在Visual Studio中将数据保存到基于服务的数据库

Question

我有一个名为NumLeter.mdf的本地Db两个表：LeterTb和NumberTb。我想插入NumberTb新值，当应用程序运行时，我插入的新值正确显示给我，好像它们已被插入，但是当关闭应用程序和显示表数据中的clic时，新数据未添加到表。我已经实现了EntityFramework v：6.1.3。这是我的代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace LearningVS
{
public partial class Form1 : Form
{
    SqlConnection conexion;

    public Form1()
    {
        InitializeComponent();
        conexion = cConexion.getConexion();
    }

    private void btInsertNum_Click(object sender, EventArgs e)
    {
         insertNumber();
    }


    public void insertNumber()
    {
        SqlCommand command = new SqlCommand();
        command.Connection = conexion;
        command.CommandText = "INSERT INTO NumberTb(numberA, numberB, numberC) VALUES(@numberA, @numberB, @numberC)";
        command.Parameters.Add("numberA", SqlDbType.Int, 3).Value = this.txNumberA.Text;
        command.Parameters.Add("numberB", SqlDbType.Int, 3).Value = this.txNumberB.Text;
        command.Parameters.Add("numberC", SqlDbType.Int, 3).Value = this.txNumberC.Text;
        command.ExecuteNonQuery();


        //testing this either
         /*SqlDataAdapter datAdapt = new SqlDataAdapter(command);
        NumLeterDataSet dtSet = new NumLeterDataSet();
        datAdapt.FillSchema(dtSet, SchemaType.Source, "NumberTb");
        datAdapt.Fill(dtSet, "NumberTb");
        datAdapt.Update(dtSet.NumberTb);*/ 
    }



    //Also I tried by creating ADO.NET Entity Data Model whit the same result
    private void button1_Click(object sender, EventArgs e)
    {
        using (var db = new NumDbModel())
        {
            var numbers = new NumberTb()
            {
                numberA = 22,
                numberB = 33,
                numberC = 44,
            };
            db.NumberTBs.Add(numbers);
            db.SaveChanges();
        }
    }
}}

这是我处理连接的地方

 namespace LearningVS
 {
  class cConexion
  {
    private static SqlConnection conexion;

    public static SqlConnection getConexion()
    {
        if (conexion != null)
        {
            return conexion;
        }
        conexion = new SqlConnection(Properties.Settings.Default.NumLetersConnectionString);
        try
        {
            conexion.Open();
            return conexion;
        }
        catch (Exception e)
        {
            System.Windows.Forms.MessageBox.Show("Error de conexión" + e.Message);
            return null;
        }
    }

    public static void cerrarConexion()
    {
        if (conexion != null)
        {
            conexion.Close();
        }
    }
}}