FormView.DataItem Proprietà

  • Riferimento

Definizione

Spazio dei nomi:
System.Web.UI.WebControls
Assembly:
System.Web.dll

Ottiene l'elemento di dati associato al controllo FormView.

public:
 virtual property System::Object ^ DataItem { System::Object ^ get(); };
[System.ComponentModel.Browsable(false)]
public virtual object DataItem { get; }
[<System.ComponentModel.Browsable(false)>]
member this.DataItem : obj
Public Overridable ReadOnly Property DataItem As Object

Valore della proprietà

Object

Un oggetto Object che rappresenta l'elemento di dati associato al controllo FormView.

Implementazioni

DataItem
Attributi
BrowsableAttribute

Esempio

Nell'esempio seguente viene illustrato come usare la DataItem proprietà per determinare il valore di un campo nell'elemento di dati.

<%@ page language="C#" %>
<%@ import namespace="System.Data"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
  
  // To dynamically create a template for a FormView control,
  // you must create a custom template class to represent 
  // the template. This template class represents the item
  // template for a FormView control.
  private sealed class EmployeeTemplate : ITemplate
  {
    
    // When implementing the ITemplate interface, you must
    // implement the InstantiateIn method. The FormView
    // control calls this method to create the template's 
    // content. 
    void ITemplate.InstantiateIn(Control container)
    {
      // Create the child controls contained in the template.
      // For this example, the item template displays the
      // FirstName and LastName fields from the data source.
      // To support data binding, create event handlers 
      // for the DataBinding event of each child child control.
      // The event handler must bind the appropriate value 
      // to the control.
      Label firstNameLabel = new Label();
      firstNameLabel.ID = "FirstNameLabel";
      firstNameLabel.DataBinding += new EventHandler(FirstNameLabel_DataBinding);
      
      LiteralControl lineBreak = new LiteralControl("<br/>");
      
      Label lastNameLabel = new Label();
      lastNameLabel.ID = "LastNameLabel";
      lastNameLabel.DataBinding += new EventHandler(LastNameLabel_DataBinding);

      // Add the controls to the Controls collection of the 
      // container control.
      container.Controls.Add(firstNameLabel);
      container.Controls.Add(lineBreak);
      container.Controls.Add(lastNameLabel);
    }
    
    // This event handler binds the value of the FirstName field
    // to the FirstNameLabel Label control displayed in the template.
    private void FirstNameLabel_DataBinding(Object sender, EventArgs e)
    {
      // Use the sender parameter to retrieve the Label control
      // being bound to data.
      Label firstNameLabelControl = (Label)sender;

      // Retrieve the value to bind to the Label control. First,
      // use the NamingContainer property to retrieve the parent 
      // control of the Label control. In this example, the parent 
      // control is the FormView control.
      FormView formViewContainer = (FormView)firstNameLabelControl.NamingContainer;
      
      // Get the data item bound to the FormView control.
      DataRowView rowView = (DataRowView)formViewContainer.DataItem;

      // Use the data item to retrieve the value of the FirstName field
      // Set the Text property of the Label control to this value.        
      firstNameLabelControl.Text = rowView["FirstName"].ToString();
    }

    // This event handler binds the value of the LastName field
    // to the LastNameLabel Label control displayed in the template.
    private void LastNameLabel_DataBinding(Object sender, EventArgs e)
    {
      // Use the sender parameter to retrieve the Label control
      // being bound to data.
      Label lastNameLabelControl = (Label)sender;

      // Retrieve the value to bind to the Label control. First,
      // use the NamingContainer property to retrieve the parent 
      // control of the Label control. In this example, the parent 
      // control is the FormView control.
      FormView formViewContainer = (FormView)lastNameLabelControl.NamingContainer;

      // Get the data item bound to the FormView control.
      DataRowView rowView = (DataRowView)formViewContainer.DataItem;

      // Use the data item to retrieve the value of the LastName field.
      // Set the Text property of the Label control to this value.         
      lastNameLabelControl.Text = rowView["LastName"].ToString();
    }
    
  }

  void Page_Load(Object sender, EventArgs e)
  {
    
    // Create a new FormView object.
    FormView employeesFormView = new FormView();
    
    // Set the FormView object's properties.
    employeesFormView.ID = "EmployeesFormView";
    employeesFormView.DataSourceID = "EmployeeSource";
    employeesFormView.AllowPaging = true;
    employeesFormView.PagerSettings.Mode = PagerButtons.NextPrevious;
    employeesFormView.HeaderText = "Employee Name";
    employeesFormView.RowStyle.BackColor = System.Drawing.Color.LightBlue;
    employeesFormView.HeaderStyle.BackColor = System.Drawing.Color.Silver;
    employeesFormView.PagerStyle.BackColor = System.Drawing.Color.Silver;

    // Create the dynamic template using the custom template class.
    employeesFormView.ItemTemplate = new EmployeeTemplate();

    // Add the FormView object to the Controls collection
    // of the PlaceHolder control.
    DetailsViewPlaceHolder.Controls.Add(employeesFormView);

  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" > 
  <head runat="server">
    <title>FormView Constructor Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>FormView Constructor Example</h3>
        
      <!-- Use a PlaceHolder control as the container for the -->
      <!-- dynamically generated FormView control.            -->       
      <asp:PlaceHolder id="DetailsViewPlaceHolder"
        runat="server"/>
            
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value   -->
      <!-- from the Web.config file.                            -->
      <asp:sqldatasource id="EmployeeSource"
        selectcommand="Select [EmployeeID], [LastName], [FirstName] From [Employees]"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>
          
    </form>
  </body>
</html>

<%@ page language="VB" %>
<%@ import namespace="System.Data"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
  
  ' To dynamically create a template for a FormView control,
  ' you must create a custom template class to represent 
  ' the template. This template class represents the item
  ' template for a FormView control.
  Private NotInheritable Class EmployeeTemplate
    Implements ITemplate
    
    ' When implementing the ITemplate interface, you must
    ' implement the InstantiateIn method. The FormView
    ' control calls this method to create the template's 
    ' content. 
    Sub InstantiateIn(ByVal container As Control) Implements ITemplate.InstantiateIn
    
      ' Create the child controls contained in the template.
      ' For this example, the item template displays the
      ' FirstName and LastName fields from the data source.
      ' To support data binding, create event handlers 
      ' for the DataBinding event of each child child control.
      ' The event handler must bind the appropriate value 
      ' to the control.
      Dim firstNameLabel As New Label()
      firstNameLabel.ID = "FirstNameLabel"
      AddHandler firstNameLabel.DataBinding, AddressOf FirstNameLabel_DataBinding
      
      Dim lineBreak As LiteralControl = New LiteralControl("<br/>")
      
      Dim lastNameLabel As New Label()
      lastNameLabel.ID = "LastNameLabel"
      AddHandler lastNameLabel.DataBinding, AddressOf LastNameLabel_DataBinding

      ' Add the controls to the Controls collection of the 
      ' container control.
      container.Controls.Add(firstNameLabel)
      container.Controls.Add(lineBreak)
      container.Controls.Add(lastNameLabel)
    End Sub
    
    ' This event handler binds the value of the FirstName field
    ' to the FirstNameLabel Label control displayed in the template.
    Private Sub FirstNameLabel_DataBinding(ByVal sender As Object, ByVal e As EventArgs)

      ' Use the sender parameter to retrieve the Label control
      ' being bound to data.
      Dim firstNameLabelControl As Label = CType(sender, Label)

      ' Retrieve the value to bind to the Label control. First,
      ' use the NamingContainer property to retrieve the parent 
      ' control of the Label control. In this example, the parent 
      ' control is the FormView control.
      Dim formViewContainer As FormView = CType(firstNameLabelControl.NamingContainer, FormView)
      
      ' Get the data item bound to the FormView control.
      Dim rowView As DataRowView = CType(formViewContainer.DataItem, DataRowView)

      ' Use the data item to retrieve the value of the FirstName field
      ' Set the Text property of the Label control to this value.        
      firstNameLabelControl.Text = rowView("FirstName").ToString()
  
    End Sub

    ' This event handler binds the value of the LastName field
    ' to the LastNameLabel Label control displayed in the template.
    Private Sub LastNameLabel_DataBinding(ByVal sender As Object, ByVal e As EventArgs)

      ' Use the sender parameter to retrieve the Label control
      ' being bound to data.
      Dim lastNameLabelControl As Label = CType(sender, Label)

      ' Retrieve the value to bind to the Label control. First,
      ' use the NamingContainer property to retrieve the parent 
      ' control of the Label control. In this example, the parent 
      ' control is the FormView control.
      Dim formViewContainer As FormView = CType(lastNameLabelControl.NamingContainer, FormView)

      ' Get the data item bound to the FormView control.
      Dim rowView As DataRowView = CType(formViewContainer.DataItem, DataRowView)

      ' Use the data item to retrieve the value of the LastName field
      ' Set the Text property of the Label control to this value.         
      lastNameLabelControl.Text = rowView("LastName").ToString()
    
    End Sub

  End Class
  
  Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
      
    ' Create a new FormView object.
    Dim employeesFormView As New FormView()
    
    ' Set the FormView object's properties.
    employeesFormView.ID = "EmployeesFormView"
    employeesFormView.DataSourceID = "EmployeeSource"
    employeesFormView.AllowPaging = True
    employeesFormView.PagerSettings.Mode = PagerButtons.NextPrevious
    employeesFormView.HeaderText = "Employee Name"
    employeesFormView.RowStyle.BackColor = System.Drawing.Color.LightBlue
    employeesFormView.HeaderStyle.BackColor = System.Drawing.Color.Silver
    employeesFormView.PagerStyle.BackColor = System.Drawing.Color.Silver

    ' Create the dynamic template using the custom template class.
    employeesFormView.ItemTemplate = New EmployeeTemplate()

    ' Add the FormView object to the Controls collection
    ' of the PlaceHolder control.
    DetailsViewPlaceHolder.Controls.Add(employeesFormView)

  End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" > 
  <head runat="server">
    <title>FormView Constructor Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>FormView Constructor Example</h3>
        
      <!-- Use a PlaceHolder control as the container for the -->
      <!-- dynamically generated FormView control.            -->       
      <asp:PlaceHolder id="DetailsViewPlaceHolder"
        runat="server"/>
            
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value   -->
      <!-- from the Web.config file.                            -->
      <asp:sqldatasource id="EmployeeSource"
        selectcommand="Select [EmployeeID], [LastName], [FirstName] From [Employees]"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>
          
    </form>
  </body>
</html>

Commenti

Utilizzare la DataItem proprietà per accedere all'elemento di dati associato al FormView controllo. L'elemento di dati viene spesso usato per accedere direttamente ai valori di campo del record corrente. Il tipo di restituito da questa proprietà varia a seconda dell'origine Object dati. Ad esempio, quando un controllo è associato al FormView controllo, viene restituito un SqlDataSourceDataRowView oggetto.

Nota

Questa proprietà è disponibile solo dopo che si è verificato il data binding. Prima che si verifichi il data binding, questa proprietà restituisce null. Questa proprietà non è applicabile anche quando il FormView controllo è in modalità di inserimento e restituisce null.

Si applica a

Vedi anche