TreeNode.SelectAction Proprietà

Definizione

Ottiene o imposta l'evento o eventi da generare quando viene selezionato un nodo.Gets or sets the event or events to raise when a node is selected.

public:
 property System::Web::UI::WebControls::TreeNodeSelectAction SelectAction { System::Web::UI::WebControls::TreeNodeSelectAction get(); void set(System::Web::UI::WebControls::TreeNodeSelectAction value); };
public System.Web.UI.WebControls.TreeNodeSelectAction SelectAction { get; set; }
member this.SelectAction : System.Web.UI.WebControls.TreeNodeSelectAction with get, set
Public Property SelectAction As TreeNodeSelectAction

Valore della proprietà

Uno dei valori di TreeNodeSelectAction.One of the TreeNodeSelectAction values. Il valore predefinito è TreeNodeSelectAction.Select.The default is TreeNodeSelectAction.Select.

Esempi

Nell'esempio di codice riportato di seguito viene illustrato come utilizzare la proprietà SelectAction per specificare l'evento che viene generato quando si fa clic su un nodo.The following code example demonstrates how to use the SelectAction property to specify which event is raised when a node is clicked.


<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  void PopulateNode(Object sender, TreeNodeEventArgs e)
  {

    // Call the appropriate method to populate a node at a particular level.
    switch(e.Node.Depth)
    {
      case 0:
        // Populate the first-level nodes.
        PopulateCategories(e.Node);
        break;
      case 1:
        // Populate the second-level nodes.
        PopulateProducts(e.Node);
        break;
      default:
        // Do nothing.
        break;
    }
    
  }

  void PopulateCategories(TreeNode node)
  {
    
    // Query for the product categories. These are the values
    // for the second-level nodes.
    DataSet ResultSet = RunQuery("Select CategoryID, CategoryName From Categories");

    // Create the second-level nodes.
    if(ResultSet.Tables.Count > 0)
    {
    
      // Iterate through and create a new node for each row in the query results.
      // Notice that the query results are stored in the table of the DataSet.
      foreach (DataRow row in ResultSet.Tables[0].Rows)
      {
        
        // Create the new node. Notice that the CategoryId is stored in the Value property 
        // of the node. This will make querying for items in a specific category easier when
        // the third-level nodes are created. 
        TreeNode newNode = new TreeNode();
        newNode.Text = row["CategoryName"].ToString(); 
        newNode.Value = row["CategoryID"].ToString();        

        // Set the PopulateOnDemand property to true so that the child nodes can be 
        // dynamically populated.
        newNode.PopulateOnDemand = true;
        
        // Set additional properties for the node.
        newNode.SelectAction = TreeNodeSelectAction.Expand;
        
        // Add the new node to the ChildNodes collection of the parent node.
        node.ChildNodes.Add(newNode);
        
      }
      
    }
    
  }

  void PopulateProducts(TreeNode node)
  {

    // Query for the products of the current category. These are the values
    // for the third-level nodes.
    DataSet ResultSet = RunQuery("Select ProductName From Products Where CategoryID=" + node.Value);

    // Create the third-level nodes.
    if(ResultSet.Tables.Count > 0)
    {
    
      // Iterate through and create a new node for each row in the query results.
      // Notice that the query results are stored in the table of the DataSet.
      foreach (DataRow row in ResultSet.Tables[0].Rows)
      {
      
        // Create the new node.
        TreeNode NewNode = new TreeNode(row["ProductName"].ToString());
        
        // Set the PopulateOnDemand property to false, because these are leaf nodes and
        // do not need to be populated.
        NewNode.PopulateOnDemand = false;
        
        // Set additional properties for the node.
        NewNode.SelectAction = TreeNodeSelectAction.None;
        
        // Add the new node to the ChildNodes collection of the parent node.
        node.ChildNodes.Add(NewNode);
        
      }
      
    }

  }

  DataSet RunQuery(String QueryString)
  {

    // Declare the connection string. This example uses Microsoft SQL Server 
    // and connects to the Northwind sample database.
    String ConnectionString = "server=localhost;database=NorthWind;Integrated Security=SSPI"; 

    SqlConnection DBConnection = new SqlConnection(ConnectionString);
    SqlDataAdapter DBAdapter;
    DataSet ResultsDataSet = new DataSet();

    try
    {

      // Run the query and create a DataSet.
      DBAdapter = new SqlDataAdapter(QueryString, DBConnection);
      DBAdapter.Fill(ResultsDataSet);

      // Close the database connection.
      DBConnection.Close();

    }
    catch(Exception ex)
    {

      // Close the database connection if it is still open.
      if(DBConnection.State == ConnectionState.Open)
      {
        DBConnection.Close();
      }
      
      Message.Text = "Unable to connect to the database.";

    }

    return ResultsDataSet;

  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>TreeView PopulateNodesFromClient Example</title>
</head>
<body>
    <form id="form1" runat="server">
    
      <h3>TreeView PopulateNodesFromClient Example</h3>
    
      <asp:TreeView id="LinksTreeView"
        Font-Names= "Arial"
        ForeColor="Blue"
        EnableClientScript="true"
        PopulateNodesFromClient="true"  
        OnTreeNodePopulate="PopulateNode"
        runat="server">
         
        <Nodes>
        
          <asp:TreeNode Text="Inventory" 
            SelectAction="Expand"  
            PopulateOnDemand="true"/>
        
        </Nodes>
        
      </asp:TreeView>
      
      <br /><br />
      
      <asp:Label id="Message" runat="server"/>

    </form>
  </body>
</html>


<%@ Page Language="VB" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  Sub PopulateNode(ByVal sender As Object, ByVal e As TreeNodeEventArgs)

    ' Call the appropriate method to populate a node at a particular level.
    Select Case e.Node.Depth

      Case 0
        ' Populate the first-level nodes.
        PopulateCategories(e.Node)

      Case 1
        ' Populate the second-level nodes.
        PopulateProducts(e.Node)

      Case Else
        ' Do nothing.

    End Select

  End Sub

  Sub PopulateCategories(ByVal node As TreeNode)

    ' Query for the product categories. These are the values
    ' for the second-level nodes.
    Dim ResultSet As DataSet = RunQuery("Select CategoryID, CategoryName From Categories")

    ' Create the second-level nodes.
    If ResultSet.Tables.Count > 0 Then

      ' Iterate through and create a new node for each row in the query results.
      ' Notice that the query results are stored in the table of the DataSet.
      Dim row As DataRow

      For Each row In ResultSet.Tables(0).Rows

        ' Create the new node. Notice that the CategoryId is stored in the Value property 
        ' of the node. This will make querying for items in a specific category easier when
        ' the third-level nodes are created. 
        Dim newNode As TreeNode = New TreeNode()
        Newnode.Text = row("CategoryName").ToString() 
        Newnode.Value = row("CategoryID").ToString()

        ' Set the PopulateOnDemand property to true so that the child nodes can be 
        ' dynamically populated.
        newNode.PopulateOnDemand = True

        ' Set additional properties for the node.
        newNode.SelectAction = TreeNodeSelectAction.Expand

        ' Add the new node to the ChildNodes collection of the parent node.
        node.ChildNodes.Add(newNode)

      Next

    End If

  End Sub

  Sub PopulateProducts(ByVal node As TreeNode)

    ' Query for the products of the current category. These are the values
    ' for the third-level nodes.
    Dim ResultSet As DataSet = RunQuery("Select ProductName From Products Where CategoryID=" & node.Value)

    ' Create the third-level nodes.
    If ResultSet.Tables.Count > 0 Then

      ' Iterate through and create a new node for each row in the query results.
      ' Notice that the query results are stored in the table of the DataSet.
      Dim row As DataRow

      For Each row In ResultSet.Tables(0).Rows

        ' Create the new node.
        Dim NewNode As TreeNode = New TreeNode(row("ProductName").ToString())

        ' Set the PopulateOnDemand property to false, because these are leaf nodes and
        ' do not need to be populated.
        NewNode.PopulateOnDemand = False

        ' Set additional properties for the node.
        NewNode.SelectAction = TreeNodeSelectAction.None

        ' Add the new node to the ChildNodes collection of the parent node.
        node.ChildNodes.Add(NewNode)

      Next

    End If

  End Sub

  Function RunQuery(ByVal QueryString As String) As DataSet

    ' Declare the connection string. This example uses Microsoft SQL Server 
    ' and connects to the Northwind sample database.
    Dim ConnectionString As String = "server=localhost;database=NorthWind;Integrated Security=SSPI"

    Dim DBConnection As SqlConnection = New SqlConnection(ConnectionString)
    Dim DBAdapter As SqlDataAdapter
    Dim ResultsDataSet As DataSet = New DataSet

    Try

      ' Run the query and create a DataSet.
      DBAdapter = New SqlDataAdapter(QueryString, DBConnection)
      DBAdapter.Fill(ResultsDataSet)

      ' Close the database connection.
      DBConnection.Close()

    Catch ex As Exception

      ' Close the database connection if it is still open.
      If DBConnection.State = ConnectionState.Open Then

        DBConnection.Close()

      End If

      Message.Text = "Unable to connect to the database."

    End Try

    Return ResultsDataSet

  End Function

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>TreeView PopulateNodesFromClient Example</title>
</head>
<body>
    <form id="form1" runat="server">
    
      <h3>TreeView PopulateNodesFromClient Example</h3>
    
      <asp:TreeView id="LinksTreeView"
        Font-Names= "Arial"
        ForeColor="Blue"
        EnableClientScript="true"
        PopulateNodesFromClient="true"  
        OnTreeNodePopulate="PopulateNode"
        runat="server">
         
        <Nodes>
        
          <asp:TreeNode Text="Inventory" 
            SelectAction="Expand"  
            PopulateOnDemand="true"/>
        
        </Nodes>
        
      </asp:TreeView>
      
      <br /><br />
      
      <asp:Label id="Message" runat="server"/>

    </form>
  </body>
</html>

Commenti

Il testo di un nodo nel controllo TreeView può essere in una delle due modalità, ovvero la modalità di selezione o la modalità di navigazione.The text of a node in the TreeView control can be in one of two modes: selection mode or navigation mode. Per impostazione predefinita, un nodo è in modalità di selezione.By default, a node is in selection mode. Per attivare la modalità di navigazione per un nodo, impostare la proprietà NavigateUrl del nodo su un valore diverso da una stringa vuota ("").To put a node into navigation mode, set the node's NavigateUrl property to a value other than an empty string (""). Per attivare la modalità di selezione di un nodo, impostare la proprietà NavigateUrl del nodo su una stringa vuota.To put a node into selection mode, set the node's NavigateUrl property to an empty string.

Nota

Quando un nodo è in modalità di navigazione, gli eventi di selezione vengono disabilitati per quel nodo.When a node is in navigation mode, selection events are disabled for that node. Se si fa clic su un nodo, l'utente viene indirizzato all'URL specificato, invece di inviare di nuovo la pagina al server e generare un evento.Clicking a node will direct the user to the specified URL, rather than posting the page back to the server and raising an event.

Quando un nodo è in modalità di selezione, utilizzare la proprietà SelectAction per specificare l'evento o gli eventi che vengono generati quando viene selezionato un nodo.When a node is in selection mode, use the SelectAction property to specify which event or events are raised when a node is selected. Nella tabella seguente sono elencate le opzioni disponibili.The following table lists the available options.

Azione di selezioneSelection action DescriptionDescription
TreeNodeSelectAction.Expand Consente di alternare il nodo espanso e compresso.Toggles the node between expanded and collapsed. Genera l'evento TreeNodeExpanded o l'evento TreeNodeCollapsed in base alle esigenze.Raises the TreeNodeExpanded event or the TreeNodeCollapsed event as appropriate.
TreeNodeSelectAction.None Non genera eventi quando si seleziona un nodo.Raises no events when a node is selected.
TreeNodeSelectAction.Select Genera l'evento SelectedNodeChanged quando viene selezionato un nodo.Raises the SelectedNodeChanged event when a node is selected.
TreeNodeSelectAction.SelectExpand Genera sia la SelectedNodeChanged che gli eventi TreeNodeExpanded quando viene selezionato un nodo.Raises both the SelectedNodeChanged and the TreeNodeExpanded events when a node is selected. I nodi sono espansi, mai compressi.Nodes are only expanded, never collapsed.

Nota

Non viene eseguito il rendering della proprietà HoverNodeStyle per un nodo con la relativa proprietà SelectAction impostata su TreeNodeSelectAction.None.The HoverNodeStyle property is not rendered for a node with its SelectAction property set to TreeNodeSelectAction.None.

Il valore di questa proprietà viene archiviato nello stato di visualizzazione.The value of this property is stored in view state.

Si applica a

Vedi anche