LINQ语句中的问题

Question

我要还给你一份名单。这是包含在我的xml文件中不能为空的XML节点的名称。

List<Setting> settingList = SettingsGateway.GetBySettingTypeList("VerifyField");

我有一份LINQ声明。我试图返回所有有空节点的事务。这里的列表返回不能为空的节点。有人知道我在这里做错了什么吗？

下面的代码应该将“事务”绑定到DataGrid，并显示具有所需的空节点的Txn。

var transactionList =
from transactions in root.Elements(XName.Get("Transactions")).Elements().AsEnumerable()
where transactions.Elements().Any
(
    el => 
    //String.IsNullOrEmpty(el.Value) &&
    //elementsThatCannotBeEmpty.Contains(el.Name)
    settingList.Any(
        name => String.IsNullOrEmpty(el.Element(name.SettingValue).Value)
    )
)
select new
{
    CustomerName = transactions.Element(XName.Get("CustomerName")).Value,
    ConfirmationNumber = transactions.Element(XName.Get("ConfirmationNumber")).Value
 };

 GridView.DataSource = transactionList;
 GridView.DataBind();

XML文件示例：

<OnlineBanking>
  <Transactions>
    <Txn>
      <UserName>John Smith</UserName>
      <CustomerStreet>123 Main</CustomerStreet>
      <CustomerStreet2></CustomerStreet2>
      <CustomerCity>New York</CustomerCity>
      <CustomerState>NY</CustomerState>
      <CustomerZip>12345</CustomerZip>
    </Txn>
  </Transactions>
</OnlineBanking>

Answer 1

好的，第一个问题:如果元素丢失了，您将得到一个NullReferenceException。

我建议为不能为null的元素创建一个List<string>，以简化查询。然后：

var requiredElements = settingList.Select(x => x.SettingValue).ToList();

var transactionList = root
      .Elements("Transactions")
      .Elements("Txn")
      .Where(x => requiredElements
                    .Any(name => string.IsNullOrEmpty((string) x.Element(name)));

我觉得这应该可以，而且比你原来的代码简单一点.但是老实说，你的原始代码看起来应该起作用了。它到底做了什么？你还不清楚实际的结果和预期的结果.

Answer 2

就像这样：

var transactionList =
     root
    .Elements(XName.Get("Transactions")) //Get <Transaction> elements
    .Elements() //Get <Txn> elements
    .Where(txn => txn.Elements().Any(e => e.Value == String.Empty))  //Filter <Txn> Elements if it have any element like this: <CustomerStreet2></CustomerStreet2>
    .Select(x => new {
        PropertyX = x.Element(XName.Get("UserName")),
        PropertyY = x.Element(XName.Get("CustomerStreet")),
                    ...
    });

与以下方面合作：

<OnlineBanking>
  <Transactions>
    <Txn> <!-- This one matches! -->
      <UserName>John Smith</UserName>
      <CustomerStreet>123 Main</CustomerStreet>
      <CustomerStreet2></CustomerStreet2> 
      <CustomerCity>New York</CustomerCity>
      <CustomerState>NY</CustomerState>
      <CustomerZip>12345</CustomerZip>
    </Txn>
    <Txn> <!-- This one doesn't match! -->
      <UserName>John Smith</UserName>
      <CustomerStreet>123 Main</CustomerStreet>
      <CustomerStreet2>ASDASD</CustomerStreet2>
      <CustomerCity>New York</CustomerCity>
      <CustomerState>NY</CustomerState>
      <CustomerZip>12345</CustomerZip>
    </Txn>
  </Transactions>
</OnlineBanking>