Entity Framework 基础操作(1)

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()]
    public string SchoolId { get; set; }

    [StringLength()]
    public string Name { get; set; }

    public DateTime? CreateTime { get; set; }

    [StringLength()]
    public string Address { get; set; }

    [StringLength()]
    public string Telephone { get; set; }
}

public partial class Student
{
    [StringLength()]
    public string StudentId { get; set; }

    [StringLength()]
    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() > ;
    }

    //添加
    public bool AddEntity(T entity)
    {

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

    //删除
    public bool DeleteEntity(T entity)
    {
        Db.Entry<T>(entity).State = EntityState.Deleted;
        return Db.SaveChanges() > ;
    }
    //批量添加
    public bool AddBatch(IList<T> arrObj)
    {
        Db.Set<T>().AddRange(arrObj);
        return Db.SaveChanges() > ;
    }
    //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() > ;
    }
    //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() > ;
    }
    //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 - ) * pageSize).Take<T>(pageSize);
        }
        else
        {
            temp = temp.OrderByDescending<T, s>(orderbyLambda).Skip<T>((pageIndex - ) * 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"
});