Lambda迭代过滤 [英] Lambda Iterational Filtering

问题描述

亲爱的，



我在C＃中使用lambda表达式，以便在数据库实体中进行过滤。我正在访问的表使用分层树结构，并且特定实体可以具有无限级别的子级，可以通过.Children访问，例如：



< pre lang =c＃> string name = entity.Children.First（）。Children.First（）。Children.First（）。Name;

我正在尝试查找包含给定孩子特定值的根节点。因此，例如，该方法将采用 name 参数，该参数可以是Level1.Level2.Name和 value 参数，可以是测试。



所以在这种情况下，我需要检查一个名为 Level1 的子节点，这个孩子必须包含一个名为 Level2 的孩子，它有另一个名为 Name 的孩子，其值为 Test 。





我到目前为止尝试的是这样的：

  var 谓词= PredicateBuilder.True< Attribute>（）; 
 predicate = predicate.And（a = >  a.ParentId ==  5 ）。扩大（）; 
 
  //   segments是由'。'分割成字符串[]的输入名称。字符 
  for （ int  x =  0 ; x <  segmentss.Length; x ++）
 {
  string  tmpSegment = segments [x]; 
 
 predicate = predicate.And（e = >  e.Children.Any（c =  >  c.Name.Equals（tmpSegment，StringComparison.OrdinalIgnoreCase）））。Expand（）; 
} 
 
 query = query.Where（predicate）; 
 
  //  执行查询并检索结果......  

问题是这个查询都是在基节点上进行评估的。我需要对其子女和孩子的孩子重复名称检查谓词。



如果我的问题的任何部分不清楚，请不要犹豫。



谢谢！





编辑＃1：



LinqKit已经在这个项目的其他部分使用。所以如果你有一个使用LinqKit的建议，也可以接受：）

解决方案

我终于通过从叶子开始解决问题了使用查询联接的顺序，例如：

 query = query.Join（子查询，c = >  c.ParentId，p = >  p.Id，（c，p）=  >  p）; 

无论如何，谢谢你。

Dear all,

I am using lambda expressions in C# in order to filter within a database entity. The table I am accessing is using a hierarchical tree structure and a particular entity can have infinite levels of children, which can be accessed by .Children, for example:

string name = entity.Children.First().Children.First().Children.First().Name;

I am trying to find a root node that contains a particular value for a given child. So for instance, the method will take a name parameter which can be "Level1.Level2.Name" and value parameter which can be "Test".

So in this case, I need to check for a node which has a Child named Level1, and this child must in turn contain a Child named Level2 which has another Child called Name and has the value of Test.


What I tried so far is something like this:

var predicate = PredicateBuilder.True<Attribute>();
predicate = predicate.And(a => a.ParentId == 5).Expand();

// segments is the input name split into a string[] by the '.' character
for (int x = 0; x < segments.Length; x++)
{
    string tmpSegment = segments[x];

    predicate = predicate.And(e => e.Children.Any(c => c.Name.Equals(tmpSegment, StringComparison.OrdinalIgnoreCase))).Expand();
}

query = query.Where(predicate);

// Execute query and retrieve results...

The problem is that this query is all being evaluated on the base node. I need to repeat the Name checking predicate on its Children, and the Children's Children.

If any part of my question is unclear do not hesitate to ask.

Thanks!


Edit #1:

LinqKit is already being used in other parts of this project. So if you have a suggestion that uses LinqKit, it is also acceptable :)

解决方案

I have finally solved by starting from the leaf and work myself up to the parents in order using query joins, such as:

query = query.Join(subquery, c => c.ParentId, p => p.Id, (c, p) => p);

Thank you anyway.

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