如何从层次结构列表（对象）中删除记录 [英] How to delete a record from a hierarchy list(of object)

问题描述

我将我的XML选择为IEnumerable对象，然后将其转换为List（of Object）。现在，我想在匹配的Id上从列表中搜索和删除一些记录。怎么做？



我的XML文件示例

I select my XML into IEnumerable object and then convert it into List(of Object). Now, I want to search and delete some record from the list base on matched Id. How to do that?

Example of my XML file

<?xml version="1.0" encoding="utf-8" ?>
<groups defaultIcon="resources/images/modules-icons/icon.png">
  <group title="Customer">
    <item>
      <title>Customer File</title>
      <item-icon>resources/images/modules-icons/CustomerSupplierFile48x48.png</item-icon>
      <id>customers</id>
    </item>

    <item>
      <title>Customer Group</title>
      <item-icon>resources/images/modules-icons/sink.png</item-icon>
      <id>customers</id>
    </item>

    <item>
      <title>Shipping Address</title>
      <id>customershippingaddress</id>
    </item>


  </group>
  
  <group title="Supplier">
    <item>
      <title>Suppliers Setup</title>
      <item-icon>resources/images/modules-icons/CustomerSupplierFile48x48.png</item-icon>
      <id>suppliers</id>
    </item>

    <item>
      <title>Supplier</title>
      <id>supplier</id>
    </item>

  </group>
  
  <group title="Other group">
    <item>
      <title>Inventory</title>
        <id>inventory</id>
    </item>

    <item>
      <title>Suppliers</title>
      <id>suppliers</id>
    </item>

    <item>
      <title>Help</title>
      <id>help</id>
    </item>

    <item>
      <title>Options</title>
      <id>options</id>
    </item>

    <item>
      <title>Employees</title>
      <id>employees</id>
    </item>
  </group>
</groups>

Dim document As XElement = XElement.Load(Server.MapPath("resources/MasterFiles.xml"))
         Dim defaultIcon As String = If(document.Attribute("defaultIcon") IsNot Nothing, document.Attribute("defaultIcon").Value, "")

         Dim query As IEnumerable(Of Object) = From g In document.Elements("group")
                                               Select New With {
                                                    .Title = If(g.Attribute("title") IsNot Nothing, g.Attribute("title").Value, ""),
                                                    .Items = (From i In g.Elements("item")
                                                              Select New With {

                                                             .Title = 
If(i.Element("title") IsNot Nothing, i.Element("title").Value, ""),
                                                             .Icon = If(i.Element("item-icon") IsNot Nothing, i.Element("item-icon").Value, defaultIcon),
                                                             .Id = If(i.Element("id") IsNot Nothing, i.Element("id").Value, ""),
                                                             .Visible = "Y"
                                                       })
                                            }

         ''Then convert it into List() for easy manage
         ''
         Dim qlist As List(Of Object) = query.ToList()

这是我尝试但确实知道如何删除匹配的记录

Here is what I try but do know how to delete the matched record

   For x = qlist.Count - 1 To 0 Step -1
                'Loop tru And get user module access
                For Each itm In qlist(x).Items
                    If itm.Id = "customershippingaddress" Then
'I can find it but how to do next?

                    End If
                Next
            Next

我尝试了什么：

What I have tried:

   For x = qlist.Count - 1 To 0 Step -1
                'Loop tru And get user module access
                For Each itm In qlist(x).Items
                    If itm.Id = "customershippingaddress" Then
'I can find it but how to do next?

                    End If
                Next
            Next

推荐答案

你不能删除For Each循环中列表中的项目 - 它会改变你循环的列表，并且总是会抛出异常，而且非常正确。

将For Each改为For，并从最后到开头向后工作，你可以将它们删除。

或者，设置一个新的List并添加你要删除的每个项目然后使用第二个For Each循环来调用List。删除每个人。



没有任何线索可以做到正确，我在这里寻求帮助。

将For Each改为For，然后从最后到开始向后工作，你可以将它们删除。



嗯，你知道如何将For Each改为For：

You can't delete items in a list inside a For Each loop - it changes the list you are loop ingon, and that will always throw an exception, and very rightly.
Change your For Each to a For, and work backwards from the end to the beginning and you can delete them fine.
Alternatively, set up a new List and add each item you want to remove to that and then use a second For Each loop to call List.Remove for each of them.

" have no clue to get it right and I am seeking for help here.
"Change your For Each to a For, and work backwards from the end to the beginning and you can delete them fine.""

Well, you know how to change a For Each to a For:

Dim myList As New List(Of String)()
For Each s As String In myList
    Console.WriteLine(s)
Next

成为：

Becomes:

Dim myList As New List(Of String)()
For i As Integer = 0 To myList.Length - 1
	Dim s As String = myList(i)
	Console.WriteLine(s)
Next

是吗？

所以写下For，它从最高指数运行到最低：

Yes?
So write the For so it runs from the highest index to the lowest:

Dim myList As New List(Of String)()
For i As Integer = myList.Length - 1 To 0 Step -1
	Dim s As String = myList(i)
	Console.WriteLine(s)
Next

这样，当你删除一个项目时，它不会改变你将看到的下一个项目的索引：

That way, when you delete an item it doesn't alter the index of the next item you will look at:

Dim myList As New List(Of String)()
For i As Integer = myList.Length - 1 To 0 Step -1
	Dim s As String = myList(i)
	If s.StartsWith("Delete me") Then
		myList.Remove(s)
	End If
Next

有意义吗？

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