对数据集执行 XPath 查询

2025-06-22

同步DataSet与XmlDataDocument之间的关系使您可以使用 XML 服务（如 XML 路径语言（XPath）查询），这些服务访问XmlDataDocument，并且在执行某些功能时比直接访问DataSet更方便。例如，与其使用Select方法来导航DataTable中与其他表的关系，不如对与数据集同步的XmlDataDocument执行XPath查询，以获取一份以形式表示的XML元素列表。然后，可以将 XmlNodeList 中的节点转换为XmlElement节点，传递给 XmlDataDocument 的 GetRowFromElement 方法，以返回对同步DataRow中表行的匹配引用。

例如，以下代码示例执行“孙级”XPath 查询。 数据集填充了三个表：Customers、Orders 和 OrderDetails。在此示例中，首先在 Customers 和 Orders 表之间以及 Orders 和 OrderDetails 表之间创建父子关系。然后，执行 XPath 查询以返回 Customers 节点的 XmlNodeList，其中子级 OrderDetails 节点具有值为 43 的 ProductID 节点。从本质上讲，该示例使用 XPath 查询来确定哪些客户已订购的产品，其 ProductID 为 43。

' Assumes that connection is a valid SqlConnection.  
connection.Open()  
Dim dataSet As DataSet = New DataSet("CustomerOrders")  
Dim customerAdapter As SqlDataAdapter = New SqlDataAdapter( _  
  "SELECT * FROM Customers", connection)  
customerAdapter.Fill(dataSet, "Customers")  
  
Dim orderAdapter As SqlDataAdapter = New SqlDataAdapter( _  
  "SELECT * FROM Orders", connection)  
orderAdapter.Fill(dataSet, "Orders")  
  
Dim detailAdapter As SqlDataAdapter = New SqlDataAdapter( _  
  "SELECT * FROM [Order Details]", connection)  
detailAdapter.Fill(dataSet, "OrderDetails")  
  
connection.Close()  
  
dataSet.Relations.Add("CustOrders", _  
dataSet.Tables("Customers").Columns("CustomerID"), _  
dataSet.Tables("Orders").Columns("CustomerID")).Nested = true  
  
dataSet.Relations.Add("OrderDetail", _  
  dataSet.Tables("Orders").Columns("OrderID"), _  
dataSet.Tables("OrderDetails").Columns("OrderID"), false).Nested = true  
  
Dim xmlDoc As XmlDataDocument = New XmlDataDocument(dataSet)
  
Dim nodeList As XmlNodeList = xmlDoc.DocumentElement.SelectNodes( _  
  "descendant::Customers[*/OrderDetails/ProductID=43]")  
  
Dim dataRow As DataRow  
Dim xmlNode As XmlNode  
  
For Each xmlNode In nodeList  
  dataRow = xmlDoc.GetRowFromElement(CType(xmlNode, XmlElement))  
  
  If Not dataRow Is Nothing then Console.WriteLine(xmlRow(0).ToString())  
Next

// Assumes that connection is a valid SqlConnection.  
connection.Open();  
  
DataSet dataSet = new DataSet("CustomerOrders");  
  
SqlDataAdapter customerAdapter = new SqlDataAdapter(  
  "SELECT * FROM Customers", connection);  
customerAdapter.Fill(dataSet, "Customers");  
  
SqlDataAdapter orderAdapter = new SqlDataAdapter(  
  "SELECT * FROM Orders", connection);  
orderAdapter.Fill(dataSet, "Orders");  
  
SqlDataAdapter detailAdapter = new SqlDataAdapter(  
  "SELECT * FROM [Order Details]", connection);  
detailAdapter.Fill(dataSet, "OrderDetails");  
  
connection.Close();  
  
dataSet.Relations.Add("CustOrders",  
  dataSet.Tables["Customers"].Columns["CustomerID"],  
 dataSet.Tables["Orders"].Columns["CustomerID"]).Nested = true;  
  
dataSet.Relations.Add("OrderDetail",  
  dataSet.Tables["Orders"].Columns["OrderID"],  
  dataSet.Tables["OrderDetails"].Columns["OrderID"],
  false).Nested = true;  
  
XmlDataDocument xmlDoc = new XmlDataDocument(dataSet);
  
XmlNodeList nodeList = xmlDoc.DocumentElement.SelectNodes(  
  "descendant::Customers[*/OrderDetails/ProductID=43]");  
  
DataRow dataRow;  
foreach (XmlNode xmlNode in nodeList)  
{  
  dataRow = xmlDoc.GetRowFromElement((XmlElement)xmlNode);  
  if (dataRow != null)  
    Console.WriteLine(dataRow[0]);  
}

通过

对数据集执行 XPath 查询

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