Entity Framework 基础操作

Posted 2022-04-30 vvvvljs

EF是微软推出的官方ORM框架，默认防注入可以配合LINQ一起使用，更方便开发人员。

首先通过SQLSERVER现在有的数据库类生产EF

右键-》添加-》新建项，选择AOD.NET实体数据模型，来自数据库的Code FIrst

完成添加后会生成多个文件，并且在你的项目的配置文件中有数据库的链接字符串，下面文件中 “name=Test”,

Test就是连接字符串的name

public partial class TestDB : DbContext

    public TestDB()
        : base("name=Test")
    
    

    public virtual DbSet<School> School  get; set; 
    public virtual DbSet<Student> Student  get; set; 

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    

public partial class School

    [StringLength(50)]
    public string SchoolId  get; set; 

    [StringLength(50)]
    public string Name  get; set; 

    public DateTime? CreateTime  get; set; 

    [StringLength(100)]
    public string Address  get; set; 

    [StringLength(50)]
    public string Telephone  get; set; 

public partial class Student

    [StringLength(50)]
    public string StudentId  get; set; 

    [StringLength(50)]
    public string Name  get; set; 

School和Student就是根据数据库表来生成的类

通过泛型来做基础操作

class BaseDB<T> where T : class, new()

    DbContext Db = new Test();

    //查询
    public IQueryable<T> LaodEntities(System.Linq.Expressions.Expression<Func<T, bool>> whereLambda)
    
        return Db.Set<T>().Where<T>(whereLambda);
    

    //更新
    public bool EditEntity(T entity)
    
        Db.Entry<T>(entity).State = EntityState.Modified;
        return Db.SaveChanges() > 0;
    

    //添加
    public bool AddEntity(T entity)
    

        Db.Set<T>().Add(entity);
        return Db.SaveChanges() > 0;
    

    //删除
    public bool DeleteEntity(T entity)
    
        Db.Entry<T>(entity).State = EntityState.Deleted;
        return Db.SaveChanges() > 0;
    
    //批量添加
    public bool AddBatch(IList<T> arrObj)
    
        Db.Set<T>().AddRange(arrObj);
        return Db.SaveChanges() > 0;
    
    //批量更改
    public bool UpdateBatch(IList<T> arrObj)
    
        foreach (var item in arrObj)
        
            Db.Entry<T>(item).State = EntityState.Modified;
        
        return Db.SaveChanges() > 0;
    
    //批量删除
    public bool DeleteBatch(IList<T> arrObj)
    
        foreach (var item in arrObj)
        
            Db.Entry<T>(item).State = EntityState.Deleted;
        
        return Db.SaveChanges() > 0;
    
    //分页
    public IQueryable<T> LoadPageEntities<s>(int pageIndex, int pageSize, out int totalCount, System.Linq.Expressions.Expression<Func<T, bool>> whereLambda, System.Linq.Expressions.Expression<Func<T, s>> orderbyLambda, bool isAsc)
    
        var temp = Db.Set<T>().Where<T>(whereLambda);
        totalCount = temp.Count();
        if (isAsc)//升序
        
            temp = temp.OrderBy<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);
        
        else
        
            temp = temp.OrderByDescending<T, s>(orderbyLambda).Skip<T>((pageIndex - 1) * pageSize).Take<T>(pageSize);
        
        return temp;
    

实际使用

BaseDB<Student> baseDB = new BaseDB<Student>();
baseDB.AddEntity(new Student 
    StudentId = Guid.NewGuid().ToString(),
    Name = "小红"
);