EF code frist 使用Linq或者Sql执行

时间：2018-12-04 11:39:47 阅读：248 评论：0 收藏：0 [点我收藏+]

标签：sele ges ons 一个 border not foreach class start

1.使用Linq查询

using (var db = new BloggingContext())
{
#region 使用linq查询
Console.Write("Enter a name for a new Blog: ");
var name = Console.ReadLine();
var blog = new Blog { Name = name };
db.Blogs.Add(blog);
db.SaveChanges();
var query = from b in db.Blogs
orderby b.Name
select b;
Console.WriteLine("All blogs in the database:");
foreach (var item in query)
{
Console.WriteLine(item.Name);
}
Console.WriteLine("Press any key to exit...");
Console.ReadKey();
#endregion

2. 使用sql语句查询

2.1 执行存储过程

List<Post> Posts = db.Database.SqlQuery<Post>("TestProcedure @personId", new SqlParameter("@personId", "1000")).ToList();
foreach (var item in Posts)
{
Console.WriteLine("{0} {1} {2} {3}", item.BlogId, item.Content, item.PostId, item.Title);
}

2.2 执行普通sql语句查询

var blogs = db.Database.SqlQuery<Blog>("select * from Blogs where Name = @name", new SqlParameter("name", "gjp"));
foreach (var item in blogs)
{
Console.WriteLine("ID:{0},Name:{1}", item.BlogId, item.Name);
}
Console.ReadKey();

2.3 使用sql语言更新，删除，增加操作可以使用ExecuteSqlCommand方法

var items = db.Blogs.ToList();
int id;
foreach (var item in items)
{
id = item.BlogId;
break;
}
Console.WriteLine("执行sql，更改");
int count = db.Database.ExecuteSqlCommand("update Blogs set Name = @content where BlogId = @postid", new SqlParameter[] { new SqlParameter("@content", "shjgshgujsjgjkagj"), new SqlParameter("@postid", 1) });
if (count == 1)
{
db.SaveChanges();
Console.WriteLine("Sql执行成功");
foreach (var item in db.Blogs)
{
Console.WriteLine("ID:{0},Name:{1}", item.BlogId, item.Name);
}
}
Console.WriteLine("是否继续？yes/no。将值改回来");
if (Console.ReadLine() == "yes")
{
int count1 = db.Database.ExecuteSqlCommand("update Blogs set Name = @content where BlogId = @postid", new SqlParameter[] { new SqlParameter("@content", "gjp"), new SqlParameter("@postid", 1) });
if (count1 == 1)
{
db.SaveChanges();
Console.WriteLine("sql执行成功");
foreach (var item in db.Blogs)
{
Console.WriteLine("ID:{0},Name:{1}", item.BlogId, item.Name);
}
}
Console.WriteLine("按任意键继续");
Console.ReadKey();
}

3 code first 控制数据库

1）会在没有数据库时创建一个，这是默认行为

Database.SetInitializer( new CreateDatabaseIfNotExists<BreakAwayContext>());

2）模型改变时，自动重新创建一个新的数据库

Database.SetInitializer( new DropCreateDatabaseIfModelChanges<BreakAwayContext>());

3）每次运行时都重新生成数据库

Database.SetInitializer(new DropCreateDatabaseAlways<BreakAwayContext>());

3.code first创建

1）首先打开“程序保管理器控制台”

技术分享图片

2）输入"Enable-Migrations",用于启用项目“code frist”迁移

技术分享图片

3)然后创建Model，Context等

public class Blog
{
public int BlogId { get; set; }
public string Name { get; set; }

public virtual List<Post> Posts { get; set; }
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }

public int BlogId { get; set; }
public virtual Blog Blog { get; set; }
}
public class BloggingContext:DbContext
{
public DbSet<Blog> Blogs { get; set; }
public DbSet<Post> Posts { get; set; }
}

4）此时执行“控制台程序”就行了，ef已帮你自动创建好数据库了

4 把Code First应用于已经存在的数据库

1)创建“Ado.net实体数据模型”