2

我有一个如下所示的实体结构，我在这里所做的是基于输入找到主实体，然后通过导航属性找到子实体，然后从不同位置的子表中删除子实体

public class GlazingOrGasMaterial : AEIMasterBase
{
    [ForeignKey("SourceOfData"), GraphQLIgnore]
    public Guid? SourceOfDataId { get; set; }
    public virtual CodeStandardGuideline SourceOfData { get; set; }
    [ForeignKey("GlazingComplexMaterial"), GraphQLIgnore]
    public Guid? GlazingComplexMaterialId { get; set; }
    [ForeignKey("GlazingSimpleMaterial"), GraphQLIgnore]
    public Guid? GlazingSimpleMaterialId { get; set; }
    [ForeignKey("GlazingGasMaterial"), GraphQLIgnore]
    public Guid? GlazingGasMaterialId { get; set; }
    public virtual GlazingComplexMaterial GlazingComplexMaterial { get; set; }
    public virtual GlazingSimpleMaterial GlazingSimpleMaterial { get; set; }
    public virtual GlazingGasMaterial GlazingGasMaterial { get; set; }
}

以下是删除该子实体的代码

方法一：

   if(requestInput.RequestType == RequestAction.EDIT)
    {
        var existingGlazingOrGasMaterial = dbContext.GlazingOrGasMaterials.Find(requestInput.DataId);
        if(existingGlazingOrGasMaterial != default)
        {
            var existingGasMaterial = dbContext.GlazingGasMaterials.SingleOrDefault(gasMaterial => gasMaterial.Id == existingGlazingOrGasMaterial.GlazingGasMaterialId);
            if(existingGasMaterial != default)
            {
                dbContext.GlazingGasMaterials.Remove(existingGasMaterial);
            }
        }
    }

下面是我删除该子实体的代码

方法二：

    if (requestInput.RequestType == RequestAction.EDIT)
    {
        var existingGlazingOrGasMaterial = dbContext.GlazingOrGasMaterials.Find(requestInput.DataId);
        if (existingGlazingOrGasMaterial != default)
        {
            var existingComplexMaterial = dbContext.GlazingComplexMaterials.SingleOrDefault(complexMaterial => complexMaterial.Id == existingGlazingOrGasMaterial.GlazingComplexMaterialId);
            if (existingComplexMaterial != default)
            {
                dbContext.GlazingComplexMaterials.Remove(existingComplexMaterial);
            }
        }
    }

方法三：

    if (requestInput.RequestType == RequestAction.EDIT)
    {
        var existingGlazingOrGasMaterial = dbContext.GlazingOrGasMaterials.Find(requestInput.DataId);
        if (existingGlazingOrGasMaterial != default)
        {
            var existingSimpleMaterial = dbContext.GlazingSimpleMaterials.SingleOrDefault(simpleMaterial => simpleMaterial.Id == existingGlazingOrGasMaterial.GlazingSimpleMaterialId);
            if (existingSimpleMaterial != default)
            {
                dbContext.GlazingSimpleMaterials.Remove(existingSimpleMaterial);
            }
        }
    }

下面是子实体的结构

public class GlazingSimpleMaterial 
{
    public Guid Id { get; set; }
    .....
    .....
}
public class GlazingComplexMaterial 
{
    public Guid Id { get; set; }
    .....
    .....
}
public class GlazingGasMaterial 
{
    public Guid Id { get; set; }
    .....
    .....
}

我正在寻找一种通用方法，我们可以将实体作为泛型类型传递并进行删除，有人可以告诉我如何实现这一点吗？

提前谢谢了！！

4

3 回答 3

3

然后通过导航属性找到子实体

您无需手动执行此操作，EF Core 可以使用加载相关数据的可用方法为您执行此操作- 急切、显式或惰性。在这种特殊情况下，预加载可能是最合适的，因为它允许您将前两个步骤（查找主实体和关联的子实体）与单个数据库请求结合在一起。

无论您选择哪种查找子实体的方法，所讨论的方法的概括都是提供导航属性访问器表达式 ( Expression<Func<TParent, TChild>>)，这足以执行当前代码的等效操作。

例如，假设GlazingOrGasMaterial.Id属性类型是Guid并且来自AEIMasterBase类，主体可以概括为

public static void RemoveChild<TParent, TChild>(
    DbContext db,
    Guid parentId,
    Expression<Func<TParent, TChild>> childReference // <--
)
    where TParent : AEIMasterBase
    where TChild : class
{
    var parent = db.Set<TParent>()
        .Include(childReference) // <--
        .FirstOrDefault(p => p.Id == parentId);
    if (parent != null)
    {
        var child = db.Entry(parent)
            .Reference(childReference) // <--
            .CurrentValue;
        if (child != null)
            db.Remove(child);
    }
}

但是现在可以很容易地看出您并不真的需要父实体，因此可以将实现简化（也变得更高效）如下（相同的方法签名）：

var child = db.Set<TParent>()
    .Where(p => p.Id == parentId)
    .Select(childReference) // <--
    .FirstOrDefault();
if (child != null)
    db.Remove(child);

在这两种情况下，这 3 个电话都是

if (requestInput.RequestType == RequestAction.EDIT)
    RemoveChild(dbContext, requestInput.DataId, (GlazingOrGasMaterial m) => m.{NavigationProperty});

m.{NavigationProperty}分别m.GlazingGasMaterial在哪里m.GlazingComplexMaterial和m.GlazingSimpleMaterial

于 2020-11-02T07:34:49.533 回答
2

首先，让我们加快您的查询速度

if (requestInput.RequestType == RequestAction.EDIT)
{
    var query = 
       from m in dbContext.GlazingOrGasMaterials
       join gasMaterial in dbContext.GlazingGasMaterials on m.GlazingGasMaterialId equals gasMaterial.Id
       where m.Id == requestInput.DataId
       select gasMaterial;

    var existingGasMaterial = query.FirstOrDefault();

    if (existingGasMaterial != default)
    {
        dbContext.GlazingGasMaterials.Remove(existingGasMaterial);
    }
}
于 2020-11-01T23:23:25.047 回答
2

如果你要盲目地删除一些东西，你不需要先从数据库中加载它；

dbContext.GlazingGasMaterials.Remove(
    new GlazingOrGasMaterials{
        Id = existingGlazingOrGasMaterial.GlazingGasMaterialId
    });

假设您的类型实现了一个通用接口来定义它们的主键，您可以概括上述内容；

public static void Remove<T>(this DbContext context, Guid Id) where T:IPrimaryKey, new() =>
dbContext.Set<T>.Remove(
    new T{
        Id = Id
    });

虽然这并没有那么简化你的代码。

于 2020-11-01T23:40:46.283 回答