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概念

ISoftDelete即軟刪除，資料在進行delete後不會從資料庫清除，而只是標記一個狀態，在業務範圍裡都不能獲取到這個資料，這在ORM框架裡還是比較容易實現的，對傳統的ado來說需要對sql統一進行攔截和條件過濾．

實施步驟

1. 實體繼承ISoftDelete
2. 資料上下文實現對IsDeleted的過濾
3. 對刪除方法進行調整，新增對ISoftDelete的支援

程式碼實現

1 實體繼承ISoftDelete

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    
 
foreach (var entityType in modelBuilder.Model.GetEntityTypes())
    {
        // 1. Add the IsDeleted property
        entityType.GetOrAddProperty("IsDeleted", typeof(bool));

        // 2. Create the query filter
        var parameter = Expression.Parameter(entityType.ClrType);

        // 3. EF.Property<bool>(post, "IsDeleted")
 

        var propertyMethodInfo = typeof(EF).GetMethod("Property").MakeGenericMethod(typeof(bool));
        var isDeletedProperty = Expression.Call(propertyMethodInfo, parameter, Expression.Constant("IsDeleted"));

        // 4. EF.Property<bool>(post, "IsDeleted") == false
        BinaryExpression compareExpression = Expression.MakeBinary(ExpressionType.Equal, isDeletedProperty, Expression.Constant(false
 
));

        // 5. post => EF.Property<bool>(post, "IsDeleted") == false
        var lambda = Expression.Lambda(compareExpression, parameter);

        modelBuilder.Entity(entityType.ClrType).HasQueryFilter(lambda);

2 資料上下文實現對IsDeleted的過濾

public class ProductInfo : EntityBase, ISoftDelete
{
    public string Title { get; set; }
    public decimal Amount { get; set; }
    public int Discount { get; set; }
    public int Inventory { get; set; }
    public DateTime DeletedDate { get; set; }
    public string DeletedUser { get; set; }
    public bool IsDeleted { get; set; }

    /// <summary>
    /// domain method
    /// </summary>
    /// <returns></returns>
    public decimal GetSaleAmount()
    {
        return Amount * Discount / 100;
    }
}

3 對刪除方法進行調整，新增對ISoftDelete的支援

程式碼來自Lind.DotNetCore.Repository.EFRepository型別

public void Delete(TEntity item)
{
    if (item != null)
    {
        if (typeof(ISoftDelete).IsAssignableFrom(item.GetType()))
        {
            Db.Entry(item).State = EntityState.Modified;
            var delEntity = item as ISoftDelete;
            delEntity.DeletedDate = DateTime.Now;
            delEntity.IsDeleted = true;
        }
        else
        {
            //物理刪除
            Db.Set<TEntity>().Attach(item as TEntity);
            Db.Entry(item).State = EntityState.Deleted;
            Db.Set<TEntity>().Remove(item as TEntity);
        }
        this.SaveChanges();
    }
}

上面幾行程式碼實現了對軟刪除的完整支援，從ISoftDelete介面到資料上下文裡的過濾IsDeleted，再到優化後的Delete()方法，一切看上去都很優雅！

對於軟刪除支援的框架也很多，像abp,eshopconationer,linddotnetcore等！

歡迎大家的閱讀與思考！

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