EF Core 三 、 EF Core CRUD
阿新 • • 發佈：2020-11-23
# EF Core CRUD
上篇文章中，我們已經基本入門了EFCore，搭建了一個簡單的EFCore專案，本文開始簡單使用下EF，做增刪改查的相關操作；
## 一、資料新增操作（C）
``` C#
public static async void Insert_測試新增資料1()
{
var myDbContext = new MyDbContext();
if (myDbContext.TestTables.Any(p => p.Id == 1)) return;
var newEntity = new TestTable
{
Id = 1,
Name = "主表資料1"
};
await myDbContext.TestTables.AddAsync(newEntity);
myDbContext.SaveChanges();
Console.WriteLine($"TestTable Insert Success");
Console.WriteLine($"------------------------");
}
```
是不是很簡單的程式碼？so eays ...
我們還是來分析下整體程式碼的執行；
**1.首先我們自己在程式碼段中新增了一個實體物件，並對其欄位做賦值，然後通過Add方法加入到DbSet中
2.通過DbContext.SaveChanges提交資料到資料庫儲存**
那EF是如何偷偷的在背後幫我們完成這一切的呢？
**EFCore實體四狀態，** 如下四種狀態；
``` C#
public enum EntityState
{
///
/// The entity is not being tracked by the context.
///
Detached = 0,
///
/// The entity is being tracked by the context and exists in the database. Its property
/// values have not changed from the values in the database.
///
Unchanged = 1,
///
/// The entity is being tracked by the context and exists in the database. It has been marked
/// for deletion from the database.
///
/// The entity is being tracked by the context and exists in the database. Some or all of its
/// property values have been modified.
///
Modified = 3,
///
/// The entity is being tracked by the context but does not yet exist in the database.
///