TreeNode.Value Özellik

  • Başvuru

Tanım

Ad Alanı:
System.Web.UI.WebControls
Bütünleştirilmiş Kod:
System.Web.dll

Geri gönderme olaylarını işlemek için kullanılan veriler gibi düğümle ilgili ek verileri depolamak için kullanılan görüntülenmeyen bir değeri alır veya ayarlar.

public:
 property System::String ^ Value { System::String ^ get(); void set(System::String ^ value); };
public string Value { get; set; }
member this.Value : string with get, set
Public Property Value As String

Özellik Değeri

String

Görüntülenmeyen düğümle ilgili ek veriler. Varsayılan değer boş bir dizedir ("").

Örnekler

Aşağıdaki kod örneği, anahtar alanını depolamak için özelliğinin nasıl kullanılacağını Value gösterir.


<%@ 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>

Açıklamalar

Value özelliği, düğümle ilişkili ek verileri depolayarak özelliği desteklemek Text için kullanılır. Bu değer denetimde görüntülenmez ve genellikle geri gönderme olaylarını işlemek için verileri depolamak için kullanılır.

Not

Value özelliği içeriyorsanull, get erişimci özelliğin Text değerini döndürür. Text Özelliği de içeriyorsa nullEmpty döndürülür.

Not

Aynı düzeydeki düğümlerin her biri özelliği için benzersiz bir değere Value sahip olmalıdır; TreeView denetim aynı değere sahip aynı düzeydeki farklı düğümleri ayırt edemez. Bu senaryoda, kullanıcı yinelenen değere sahip bir düğüme tıklarsa, denetimde TreeView ilk olarak görünen düğüm seçilir.

Bu özelliğin değeri görünüm durumunda depolanır.

Bu özelliğin değeri ayarlandığında, tasarımcı aracı kullanılarak otomatik olarak bir kaynak dosyasına kaydedilebilir. Daha fazla bilgi için bkz LocalizableAttribute . ve Genelleştirme ve Yerelleştirme.

Şunlara uygulanır

Ayrıca bkz.