1-实体框架数据层（基础知识）

在本文中，我们将使用一个名为 Company 的简单数据库，其中包含两个表：

[dbo]。[分类]（[CategoryID]，[CategoryName]）

[dbo]。[产品]（[ProductID]，[CategoryID]，[ProductName]）

1-1 生成实体框架代码

在这一层，我们生成实体框架代码（在项目库中）（请参阅本文 ，如何做到这一点）然后你将拥有以下类

public partial class CompanyContext : DbContext
public partial class Product
public partial class Category

1-2 创建基本界面

我们将为我们的基础功能创建一个界面

public interface IDbRepository : IDisposable
{
    #region Tables and Views functions

    IQueryable<TResult> GetAll<TResult>(bool noTracking = true) where TResult : class;
    TEntity Add<TEntity>(TEntity entity) where TEntity : class;
    TEntity Delete<TEntity>(TEntity entity) where TEntity : class;
    TEntity Attach<TEntity>(TEntity entity) where TEntity : class;
    TEntity AttachIfNot<TEntity>(TEntity entity) where TEntity : class;

    #endregion Tables and Views functions

    #region Transactions Functions

    int Commit();
    Task<int> CommitAsync(CancellationToken cancellationToken = default(CancellationToken));

    #endregion Transactions Functions

    #region Database Procedures and Functions

    TResult Execute<TResult>(string functionName, params object[] parameters);

    #endregion Database Procedures and Functions
}

1-3 实现基本接口

/// <summary>
/// Implementing basic tables, views, procedures, functions, and transaction functions
/// Select (GetAll), Insert (Add), Delete, and Attach
/// No Edit (Modify) function (can modify attached entity without function call)
/// Executes database procedures or functions (Execute)
/// Transaction functions (Commit)
/// More functions can be added if needed
/// </summary>
/// <typeparam name="TEntity">Entity Framework table or view</typeparam>
public class DbRepository : IDbRepository
{
    #region Protected Members

    protected DbContext _dbContext;

    #endregion Protected Members

    #region Constractors

    /// <summary>
    /// Repository constructor 
    /// </summary>
    /// <param name="dbContext">Entity framework databse context</param>
    public DbRepository(DbContext dbContext)
    {
        _dbContext = dbContext;

        ConfigureContext();
    }

    #endregion Constractors

    #region IRepository Implementation

    #region Tables and Views functions

    /// <summary>
    /// Query all
    /// Set noTracking to true for selecting only (read-only queries)
    /// Set noTracking to false for insert, update, or delete after select
    /// </summary>
    public virtual IQueryable<TResult> GetAll<TResult>(bool noTracking = true) where TResult : class
    {
        var entityDbSet = GetDbSet<TResult>();

        if (noTracking)
            return entityDbSet.AsNoTracking();

        return entityDbSet;
    }

    public virtual TEntity Add<TEntity>(TEntity entity) where TEntity : class
    {
        return GetDbSet<TEntity>().Add(entity);
    }

    /// <summary>
    /// Delete loaded (attached) or unloaded (Detached) entitiy
    /// No need to load object to delete it
    /// Create new object of TEntity and set the id then call Delete function
    /// </summary>
    /// <param name="entity">TEntity</param>
    /// <returns></returns>
    public virtual TEntity Delete<TEntity>(TEntity entity) where TEntity : class
    {
        if (_dbContext.Entry(entity).State == EntityState.Detached)
        {
            _dbContext.Entry(entity).State = EntityState.Deleted;
            return entity;
        }
        else
            return GetDbSet<TEntity>().Remove(entity);
    }

    public virtual TEntity Attach<TEntity>(TEntity entity) where TEntity : class
    {
        return GetDbSet<TEntity>().Attach(entity);
    }

    public virtual TEntity AttachIfNot<TEntity>(TEntity entity) where TEntity : class
    {
        if (_dbContext.Entry(entity).State == EntityState.Detached)
            return Attach(entity);

        return entity;
    }

    #endregion Tables and Views functions

    #region Transactions Functions

    /// <summary>
    /// Saves all changes made in this context to the underlying database.
    /// </summary>
    /// <returns>The number of objects written to the underlying database.</returns>
    public virtual int Commit()
    {
        return _dbContext.SaveChanges();
    }

    /// <summary>
    /// Asynchronously saves all changes made in this context to the underlying database.
    /// </summary>
    /// <param name="cancellationToken">A System.Threading.CancellationToken to observe while waiting for the task to complete.</param>
    /// <returns>A task that represents the asynchronous save operation.  The task result contains the number of objects written to the underlying database.</returns>
    public virtual Task<int> CommitAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        return _dbContext.SaveChangesAsync(cancellationToken);
    }

    #endregion Transactions Functions

    #region Database Procedures and Functions

    /// <summary>
    /// Executes any function in the context
    /// use to call database procesdures and functions
    /// </summary>>
    /// <typeparam name="TResult">return function type</typeparam>
    /// <param name="functionName">context function name</param>
    /// <param name="parameters">context function parameters in same order</param>
    public virtual TResult Execute<TResult>(string functionName, params object[] parameters)
    {
        MethodInfo method = _dbContext.GetType().GetMethod(functionName);

        return (TResult)method.Invoke(_dbContext, parameters);
    }

    #endregion Database Procedures and Functions

    #endregion IRepository Implementation

    #region IDisposable Implementation

    public void Dispose()
    {
        _dbContext.Dispose();
    }

    #endregion IDisposable Implementation

    #region Protected Functions

    /// <summary>
    /// Set Context Configuration
    /// </summary>
    protected virtual void ConfigureContext()
    {
        // set your recommended Context Configuration
        _dbContext.Configuration.LazyLoadingEnabled = false;
    }

    #endregion Protected Functions

    #region Private Functions

    private DbSet<TEntity> GetDbSet<TEntity>() where TEntity : class
    {
        return _dbContext.Set<TEntity>();
    }

    #endregion Private Functions

}