TreeNodeSelectAction Enumeration
Wichtig
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Stellt das Ereignis oder die Ereignisse dar, die ausgelöst werden sollen, wenn ein Knoten im TreeView-Steuerelement ausgewählt wird.
public enum class TreeNodeSelectActionpublic enum TreeNodeSelectActiontype TreeNodeSelectAction = Public Enum TreeNodeSelectAction- Vererbung
| Name | Wert | Beschreibung |
|---|---|---|
| Expand | 1 | Löst das TreeNodeExpanded-Ereignis aus, wenn ein Knoten ausgewählt wird. |
| None | 3 | Löst keine Ereignisse aus, wenn ein Knoten ausgewählt wird. |
| Select | 0 | Löst das SelectedNodeChanged-Ereignis aus, wenn ein Knoten ausgewählt wird. |
| SelectExpand | 2 | Löst das SelectedNodeChanged-Ereignis und das TreeNodeExpanded-Ereignis aus, wenn ein Knoten ausgewählt wird. |
Im folgenden Beispiel wird veranschaulicht, wie die TreeNodeSelectAction -Enumeration verwendet wird, um das Ereignis darzustellen, das ausgelöst wird, wenn im TreeView Steuerelement auf einen Knoten geklickt wird:
<%@ 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>
Wenn die TreeNode.NavigateUrl Eigenschaft auf einen anderen Wert als eine leere Zeichenfolge ("") festgelegt ist, wird durch Klicken auf den Knoten zur angegebenen URL navigiert. Wenn die TreeNode.NavigateUrl Eigenschaft auf eine leere Zeichenfolge festgelegt ist, verursacht das Klicken auf den Knoten ein Postback. Die TreeNode.SelectAction -Eigenschaft bestimmt die Ereignisse, die beim Postback ausgelöst werden sollen. Standardmäßig wird das TreeNode.Select Ereignis ausgelöst. Wenn die TreeNode.NavigateUrl -Eigenschaft festgelegt ist, werden keine Ereignisse ausgelöst.
Hinweis
Die TreeView.HoverNodeStyle -Eigenschaft wird nicht für einen Knoten gerendert, dessen TreeNode.SelectAction -Eigenschaft auf den None -Wert festgelegt ist.
| Produkt | Versionen |
|---|---|
| .NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
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