C# 查找和替换 XML 节点 [英] C# Find And Replace XML Nodes
问题描述
我决定采用推荐的 LINQ to XML 方法(请参阅下面的答案)，并且一切正常，除了我无法用增量中的记录替换更改的记录文件.我设法通过删除完整文件节点然后添加增量节点来使程序工作.有没有办法只交换它们?另外，虽然这个解决方案非常好，但有没有办法在不丢失 LINQ 代码的情况下减少内存使用量?这个解决方案可能仍然有效，但我愿意牺牲时间来降低内存使用率.
I decided to take the LINQ to XML approach (see the answer below) that was recommended and everything works EXCEPT that I can't replace out the changed records with the records from the incremental file. I managed to make the program work by just removing the full file node and then adding in the incremental node. Is there a way to just swap them instead? Also, while this solution is very nice, is there any way to shrink down memory usage without losing the LINQ code? This solution may still work, but I would be willing to sacrifice time to lower memory usage.
我正在尝试将两个 XML 文件(一个完整文件和一个增量文件)合并在一起.XML 文件如下所示:
I'm trying to take two XML files (a full file and an incremental file) and merge them together. The XML file looks like this:
<List>
<Records>
<Person id="001" recordaction="add">
...
</Person>
</Records>
</List>
recordaction 属性也可以是chg"表示更改或del"表示删除.我的程序的基本逻辑是:
The recordaction attribute can also be "chg" for changes or "del" for deletes. The basic logic of my program is:
1) 将完整文件读入 XmlDocument.
1) Read the full file into an XmlDocument.
2) 将增量文件读入 XmlDocument，使用 XmlDocument.SelectNodes() 选择节点，将这些节点放入字典中以便于搜索.
2) Read the incremental file into an XmlDocument, select the nodes using XmlDocument.SelectNodes(), place those nodes into a dictionary for easier searching.
3) 选择完整文件中的所有节点，循环遍历并对照包含增量记录的字典检查每个节点.如果 recordaction="chg" 或 "del" 将节点添加到列表中，则从 XmlNodeList 中删除该列表中的所有节点.最后，将recordaction="chg" 或"add" 记录从增量文件添加到完整文件中.
3) Select all the nodes in the full file, loop through and check each against the dictionary containing the incremental records. If recordaction="chg" or "del" add the node to a list, then delete all the nodes from the XmlNodeList that are in that list. Finally, add recordaction="chg" or "add" records from the incremental file into the full file.
4) 保存 XML 文件.
4) Save the XML file.
我在第 3 步中遇到了一些严重的问题.这是该函数的代码:
I'm having some serious problems with step 3. Here's the code for that function:
private void ProcessChanges(XmlNodeList nodeList, Dictionary<string, XmlNode> dictNodes)
{
XmlNode lastNode = null;
XmlNode currentNode = null;
List<XmlNode> nodesToBeDeleted = new List<XmlNode>();
// If node from full file matches to incremental record and is change or delete,
// mark full record to be deleted.
foreach (XmlNode fullNode in fullDocument.SelectNodes("/List/Records/Person"))
{
dictNodes.TryGetValue(fullNode.Attributes[0].Value, out currentNode);
if (currentNode != null)
{
if (currentNode.Attributes["recordaction"].Value == "chg"
|| currentNode.Attributes["recordaction"].Value == "del")
{
nodesToBeDeleted.Add(currentNode);
}
}
lastNode = fullNode;
}
// Delete marked records
for (int i = nodeList.Count - 1; i >= 0; i--)
{
if(nodesToBeDeleted.Contains(nodeList[i]))
{
nodeList[i].ParentNode.RemoveChild(nodesToBeDeleted[i]);
}
}
// Add in the incremental records to the new full file for records marked add or change.
foreach (XmlNode weeklyNode in nodeList)
{
if (weeklyNode.Attributes["recordaction"].Value == "add"
|| weeklyNode.Attributes["recordaction"].Value == "chg")
{
fullDocument.InsertAfter(weeklyNode, lastNode);
lastNode = weeklyNode;
}
}
}
传入的 XmlNodeList 只是从增量文件中选出的所有增量记录，而字典只是那些相同的节点，但键在 id 上，所以我不必遍历所有每次增量记录.现在，由于索引超出范围，该程序正在删除标记的记录"阶段死亡.我很确定添加增量记录"也不起作用.有任何想法吗?还有一些关于提高效率的建议会很好.我可能会遇到问题，因为它正在读取一个 250MB 的文件，该文件在内存中膨胀到 750MB，所以我想知道是否有更简单的方法来逐个节点地查看完整文件.谢谢！
The XmlNodeList being passed in is just all of the incremental records that were selected out from the incremental file, and the dictionary is just those same nodes but key'd on the id so I didn't have to loop through all of the incremental records each time. Right now the program is dying at the "Delete marked records" stage due to indexing out of bounds. I'm pretty sure the "Add in the incremental records" doesn't work either. Any ideas? Also some suggestions on making this more efficient would be nice. I could potentially run into a problem because it's reading in a 250MB file which balloons up to 750MB in memory, so I was wondering if there was an easier way to go node-by-node in the full file. Thanks!
推荐答案
这里有一个示例，说明如何使用 LINQ-to-XML 完成它.不需要字典:
Here's an example of how you might accomplish it with LINQ-to-XML. No dictionary is needed:
using System.Xml.Linq;
// Load the main and incremental xml files into XDocuments
XDocument fullFile = XDocument.Load("fullfilename.xml");
XDocument incrementalFile = XDocument.Load("incrementalfilename.xml");
// For each Person in the incremental file
foreach (XElement person in incrementalFile.Descendants("Person")) {
// If the person should be added to the full file
if (person.Attribute("recordaction").Value == "add") {
fullFile.Element("List").Element("Records").Add(person); // Add him
}
// Else the person already exists in the full file
else {
// Find the element of the Person to delete or change
var personToChange =
(from p in fullFile.Descendants("Person")
where p.Attribute("id").Value == person.Attribute("id").Value
select p).Single();
// Perform the appropriate operation
switch (person.Attribute("recordaction").Value) {
case "chg":
personToChange.ReplaceWith(person);
break;
case "del":
personToChange.Remove();
break;
default:
throw new ApplicationException("Unrecognized attribute");
}
}
}// end foreach
// Save the changes to the full file
fullFile.Save("fullfilename.xml");
如果您在运行时遇到任何问题，请告诉我，我会对其进行编辑和修复.我很确定它是正确的，但目前没有可用的 VS.
Please let me know if you have any problems running it and I'll edit and fix it. I'm pretty sure it's correct, but don't have VS available at the moment.
修复了 "chg" 情况以使用 personToChange.ReplaceWith(person) 而不是 personToChange = person.后者不会替换任何内容，因为它只是将引用从底层文档移开.
fixed the "chg" case to use personToChange.ReplaceWith(person) rather than personToChange = person. The latter doesn't replace anything, as it just shifts the reference away from the underlying document.
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