ListControl.ValueMember Eigenschaft

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Ruft den Pfad zur Eigenschaft ab, die als tatsächlicher Wert für die Elemente im ListControl verwendet werden soll, oder legt diese fest.

public:
 property System::String ^ ValueMember { System::String ^ get(); void set(System::String ^ value); };

public string ValueMember { get; set; }

member this.ValueMember : string with get, set

Public Property ValueMember As String

Eigenschaftswert

String

Eine String, die einen einzelnen Eigenschaftennamen vom DataSource-Eigenschaftswert darstellt , eine einzelner Eigenschaftennname oder eine Hierarchie mit durch Punkte getrennten Eigenschaftennamen, die in den Eigenschaftennamen des letzten datengebundenen Objekts aufgelöst wird. Der Standardwert ist eine leere Zeichenfolge ("").

Ausnahmen

ArgumentException

Der angegebene Eigenschaftspfad kann durch das Objekt, das von der DataSource-Eigenschaft angegeben wird, nicht aufgelöst werden.

Beispiele

Das folgende Codebeispiel zeigt das Laden der Daten in ein ArrayList und das Festlegen auf ValueMember eine Eigenschaft des Objekts in der Liste.

#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Windows::Forms;
using namespace System::Drawing;
using namespace System::Collections;
public ref class USState
{
private:
   String^ myShortName;
   String^ myLongName;

public:
   USState( String^ strLongName, String^ strShortName )
   {
      this->myShortName = strShortName;
      this->myLongName = strLongName;
   }

   property String^ ShortName 
   {
      String^ get()
      {
         return myShortName;
      }
   }

   property String^ LongName 
   {
      String^ get()
      {
         return myLongName;
      }

   }
};

public ref class ListBoxSample3: public Form
{
private:
   ListBox^ ListBox1;
   Label^ label1;
   TextBox^ textBox1;

public:
   ListBoxSample3()
   {
      ListBox1 = gcnew ListBox;
      label1 = gcnew Label;
      textBox1 = gcnew TextBox;
      this->ClientSize = System::Drawing::Size(307, 206 );
      this->Text = "ListBox Sample3";
      ListBox1->Location = Point(54,16);
      ListBox1->Name = "ListBox1";
      ListBox1->Size = System::Drawing::Size( 240, 130 );
      label1->Location = Point(14,150);
      label1->Name = "label1";
      label1->Size = System::Drawing::Size(40, 24);
      label1->Text = "Value";
      textBox1->Location = Point(54,150);
      textBox1->Name = "textBox1";
      textBox1->Size = System::Drawing::Size( 240, 24 );
      array<Control^>^temp2 = {ListBox1,label1, textBox1};
      this->Controls->AddRange( temp2 );

      // Populate the list box using an array as DataSource. 
      // DisplayMember is used to display just the long name of each state.
      ArrayList^ USStates = gcnew ArrayList;
      USStates->Add( gcnew USState( "Alabama","AL" ) );
      USStates->Add( gcnew USState( "Washington","WA" ) );
      USStates->Add( gcnew USState( "West Virginia","WV" ) );
      USStates->Add( gcnew USState( "Wisconsin","WI" ) );
      USStates->Add( gcnew USState( "Wyoming","WY" ) );
      ListBox1->DataSource = USStates;
      ListBox1->DisplayMember = "LongName";
      ListBox1->ValueMember = "ShortName";
      ListBox1->SelectedValueChanged += gcnew EventHandler( this, &ListBoxSample3::ListBox1_SelectedValueChanged );
      ListBox1->SetSelected(0, false);
   }

   void InitializeComponent(){}

private:
   void ListBox1_SelectedValueChanged( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      textBox1->Text="";
      if ( ListBox1->SelectedIndex != -1 )
            textBox1->Text = ListBox1->SelectedValue->ToString();
   }
};

[STAThread]
int main()
{
   Application::Run( gcnew ListBoxSample3 );
}

using System;
using System.Windows.Forms;
using System.Drawing;
using System.Collections;

namespace MyListControlSample
{
    public class ListBoxSample3 : Form
    {
        private ListBox ListBox1 = new ListBox();
        private Label label1 = new Label();
        private TextBox textBox1 = new TextBox();

        [STAThread]
        static void Main()
        {
            Application.Run(new ListBoxSample3());
        }

        public ListBoxSample3()
        {
            this.ClientSize = new Size(307, 206);
            this.Text = "ListBox Sample3";

            ListBox1.Location = new Point(54, 16);
            ListBox1.Name = "ListBox1";
            ListBox1.Size = new Size(240, 130);

            label1.Location = new Point(14, 150);
            label1.Name = "label1";
            label1.Size = new Size(40, 24);
            label1.Text = "Value";

            textBox1.Location = new Point(54, 150);
            textBox1.Name = "textBox1";
            textBox1.Size = new Size(240, 24);
            
            this.Controls.AddRange(new Control[] { ListBox1, label1, textBox1 });

            // Populate the list box using an array as DataSource.
            ArrayList USStates = new ArrayList();
            USStates.Add(new USState("Alabama", "AL"));
            USStates.Add(new USState("Washington", "WA"));
            USStates.Add(new USState("West Virginia", "WV"));
            USStates.Add(new USState("Wisconsin", "WI"));
            USStates.Add(new USState("Wyoming", "WY"));
            ListBox1.DataSource = USStates;

            // Set the long name as the property to be displayed and the short
            // name as the value to be returned when a row is selected.  Here
            // these are properties; if we were binding to a database table or
            // query these could be column names.
            ListBox1.DisplayMember = "LongName";
            ListBox1.ValueMember = "ShortName";

            // Bind the SelectedValueChanged event to our handler for it.
            ListBox1.SelectedValueChanged += 
                new EventHandler(ListBox1_SelectedValueChanged);

            // Ensure the form opens with no rows selected.
            ListBox1.ClearSelected();
        }

        private void InitializeComponent()
        {
        }

        private void ListBox1_SelectedValueChanged(object sender, EventArgs e)
        {
            if (ListBox1.SelectedIndex != -1)
            {
                textBox1.Text = ListBox1.SelectedValue.ToString();
                // If we also wanted to get the displayed text we could use
                // the SelectedItem item property:
                // string s = ((USState)ListBox1.SelectedItem).LongName;
            }
        }
    }

    public class USState
    {
        private string myShortName;
        private string myLongName;

        public USState(string strLongName, string strShortName)
        {

            this.myShortName = strShortName;
            this.myLongName = strLongName;
        }

        public string ShortName
        {
            get
            {
                return myShortName;
            }
        }

        public string LongName
        {

            get
            {
                return myLongName;
            }
        }
    }
}

Imports System.Windows.Forms
Imports System.Drawing
Imports System.Collections

Public Class ListBoxSample3
    Inherits Form

    Private ListBox1 As New ListBox()
    Private label1 As New Label()
    Private textBox1 As New TextBox()

    <STAThread()> _
    Shared Sub Main()
        Application.Run(New ListBoxSample3())
    End Sub

    Public Sub New()
        Me.ClientSize = New Size(307, 206)
        Me.Text = "ListBox Sample3"

        ListBox1.Location = New Point(54, 16)
        ListBox1.Name = "ListBox1"
        ListBox1.Size = New Size(240, 130)

        label1.Location = New Point(14, 150)
        label1.Name = "label1"
        label1.Size = New Size(40, 24)
        label1.Text = "Value"

        textBox1.Location = New Point(54, 150)
        textBox1.Name = "textBox1"
        textBox1.Size = New Size(240, 24)

        Me.Controls.AddRange(New Control() {ListBox1, label1, textBox1})

        ' Populate the list box using an array as DataSource. 
        Dim USStates As New ArrayList()
        USStates.Add(New USState("Alabama", "AL"))
        USStates.Add(New USState("Washington", "WA"))
        USStates.Add(New USState("West Virginia", "WV"))
        USStates.Add(New USState("Wisconsin", "WI"))
        USStates.Add(New USState("Wyoming", "WY"))
        ListBox1.DataSource = USStates

        ' Set the long name as the property to be displayed and the short
        ' name as the value to be returned when a row is selected.  Here
        ' these are properties; if we were binding to a database table or
        ' query these could be column names.
        ListBox1.DisplayMember = "LongName"
        ListBox1.ValueMember = "ShortName"

        ' Bind the SelectedValueChanged event to our handler for it.
        AddHandler ListBox1.SelectedValueChanged, AddressOf ListBox1_SelectedValueChanged

        ' Ensure the form opens with no rows selected.
        ListBox1.ClearSelected()
    End Sub

    Private Sub InitializeComponent()
    End Sub

    Private Sub ListBox1_SelectedValueChanged(ByVal sender As Object, ByVal e As EventArgs)
        If ListBox1.SelectedIndex <> -1 Then
            textBox1.Text = ListBox1.SelectedValue.ToString()
            ' If we also wanted to get the displayed text we could use
            ' the SelectedItem item property:
            ' Dim s = CType(ListBox1.SelectedItem, USState).LongName
        End If
    End Sub
End Class

Public Class USState
    Private myShortName As String
    Private myLongName As String

    Public Sub New(ByVal strLongName As String, ByVal strShortName As String)
        Me.myShortName = strShortName
        Me.myLongName = strLongName
    End Sub

    Public ReadOnly Property ShortName() As String
        Get
            Return myShortName
        End Get
    End Property

    Public ReadOnly Property LongName() As String
        Get
            Return myLongName
        End Get
    End Property

End Class

Hinweise

Geben Sie den Inhalt der ValueMember Eigenschaft in Fällen an, in denen Sie Daten binden.

Sie können die ValueMember -Eigenschaft löschen, indem Sie die -Eigenschaft auf eine leere Zeichenfolge ("") oder nullfestlegen.

Wenn Sie eine neue ValueMember Eigenschaft festlegen, werden die ValueMemberChanged Ereignisse und SelectedValueChanged ausgelöst.