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DataList.OnDeleteCommand-Methode: (DataListCommandEventArgs)

 

Veröffentlicht: Oktober 2016

Löst das DeleteCommand-Ereignis aus. Dadurch können Sie einen benutzerdefinierten Handler für das Ereignis bereitstellen.

Namespace:   System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

protected virtual void OnDeleteCommand(
	DataListCommandEventArgs e
)

Verwenden der OnDeleteCommand Methode geben Sie einen benutzerdefinierten Handler für das DeleteCommand Ereignis.

Die DeleteCommand -Ereignis wird ausgelöst, wenn die Delete geklickt wird für ein Element in der DataList Steuerelement.

Ein typischer Handler für das DeleteCommand Ereignis entfernt das ausgewählte Element aus der Datenquelle und dann bindet die Daten in der DataList Steuerelement.

Durch das Auslösen eines Ereignisses wird der Ereignishandler über einen Delegaten aufgerufen. Weitere Informationen finden Sie unter Gewusst wie: Verarbeiten von Ereignissen in einer Web Forms-Anwendung.

Mit der OnDeleteCommand-Methode können auch abgeleitete Klassen das Ereignis ohne Anfügen eines Delegaten behandeln. Dies ist das bevorzugte Verfahren für die Behandlung des Ereignisses in einer abgeleiteten Klasse.

Hinweise für Vererber:

Wenn Sie OnDeleteCommand in einer abgeleiteten Klasse überschreiben, müssen Sie die OnDeleteCommand-Methode der Basisklasse aufrufen, damit registrierte Delegaten das Ereignis empfangen.

Im folgenden Codebeispiel wird veranschaulicht, wie angegeben und code für die DeleteCommand Ereignis. Löscht das ausgewählte Element in der DataList steuern, wann die Delete geklickt wird.

System_CAPS_noteHinweis

Im folgenden Codebeispiel wird das Einzeldatei-Codemodell verwendet und kann nicht ordnungsgemäß funktionieren, wenn Sie direkt in eine Code-Behind-Datei kopiert. Dieses Codebeispiel muss in eine leere Textdatei kopiert werden, die einer ASPX-Erweiterung. Weitere Informationen über das Web Forms-Codemodell finden Sie unter ASP.NET Web Forms Page Code Model.


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

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>DataList Edit Example</title>
<script runat="server">

      // The Cart and CartView objects temporarily store the data source
      // for the DataList control while the page is being processed.
      DataTable Cart = new DataTable();
      DataView CartView;   

      void Page_Load(Object sender, EventArgs e) 
      {

         // With a database, use an select query to retrieve the data. 
         // Because the data source in this example is an in-memory
         // DataTable, retrieve the data from session state if it exists;
         // otherwise, create the data source.
         GetSource();

         // The DataList control maintains state between posts to the server;
         // it only needs to be bound to a data source the first time the
         // page is loaded or when the data source is updated.
         if (!IsPostBack)
         {

            BindList();

         }

      }

      void BindList() 
      {

         // Set the data source and bind to the DataList control.
         ItemsList.DataSource = CartView;
         ItemsList.DataBind();

      }

      void GetSource()
      {

         // For this example, the data source is a DataTable that 
         // is stored in session state. If the data source does not exist,
         // create it; otherwise, load the data.
         if (Session["ShoppingCart"] == null) 
         {     

            // Create the sample data.
            DataRow dr;  

            // Define the columns of the table.
            Cart.Columns.Add(new DataColumn("Qty", typeof(Int32)));
            Cart.Columns.Add(new DataColumn("Item", typeof(String)));
            Cart.Columns.Add(new DataColumn("Price", typeof(Double)));

            // Store the table in session state to persist its values 
            // between posts to the server.
            Session["ShoppingCart"] = Cart;

            // Populate the DataTable with sample data.
            for (int i = 1; i <= 9; i++) 
            {
               dr = Cart.NewRow();
               if (i % 2 != 0)
               {
                  dr[0] = 2;
               }
               else
               {
                  dr[0] = 1;
               }
               dr[1] = "Item " + i.ToString();
               dr[2] = (1.23 * (i + 1));
               Cart.Rows.Add(dr);
            }

         } 

         else
         {

            // Retrieve the sample data from session state.
            Cart = (DataTable)Session["ShoppingCart"];

         }         

         // Create a DataView and specify the field to sort by.
         CartView = new DataView(Cart);
         CartView.Sort="Item";

         return;

      }

      void Edit_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Set the EditItemIndex property to the index of the item clicked
         // in the DataList control to enable editing for that item. Be sure
         // to rebind the DataList to the data source to refresh the control.
         ItemsList.EditItemIndex = e.Item.ItemIndex;
         BindList();

      }

      void Cancel_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Set the EditItemIndex property to -1 to exit editing mode. Be sure
         // to rebind the DataList to the data source to refresh the control.
         ItemsList.EditItemIndex = -1;
         BindList();

      }

      void Delete_Command(Object sender, DataListCommandEventArgs e) 
      { 

         // Retrieve the name of the item to remove.
         String item = ((Label)e.Item.FindControl("ItemLabel")).Text;

         // Filter the CartView for the selected item and remove it from
         // the data source.
         CartView.RowFilter = "Item='" + item + "'";
         if (CartView.Count > 0) 
         {
            CartView.Delete(0);
         }
         CartView.RowFilter = "";

         // Set the EditItemIndex property to -1 to exit editing mode. Be sure
         // to rebind the DataList to the data source to refresh the control.
         ItemsList.EditItemIndex = -1;
         BindList();

      }

      void Update_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Retrieve the updated values from the selected item.
         String item = ((Label)e.Item.FindControl("ItemLabel")).Text;
         String qty = ((TextBox)e.Item.FindControl("QtyTextBox")).Text;
         String price = ((TextBox)e.Item.FindControl("PriceTextBox")).Text;

         // With a database, use an update command to update the data.
         // Because the data source in this example is an in-memory 
         // DataTable, delete the old row and replace it with a new one.

         // Filter the CartView for the selected item and remove it from
         // the data source.
         CartView.RowFilter = "Item='" + item + "'";
         if (CartView.Count > 0)
         {
            CartView.Delete(0);
         }
         CartView.RowFilter = "";

         // ***************************************************************
         // Insert data validation code here. Make sure to validate the
         // values entered by the user before converting to the appropriate
         // data types and updating the data source.
         // ***************************************************************

         // Add a new entry to replace the previous item.
         DataRow dr = Cart.NewRow();
         dr[0] = qty;
         dr[1] = item;
         // If necessary, remove the '$' character from the price before
         // converting the price to a Double.
         if(price[0] == '$')
         {
            dr[2] = Convert.ToDouble(price.Substring(1));
         }
         else
         {
            dr[2] = Convert.ToDouble(price);
         }
         Cart.Rows.Add(dr);

         // Set the EditItemIndex property to -1 to exit editing mode. 
         // Be sure to rebind the DataList to the data source to refresh
         // the control.
         ItemsList.EditItemIndex = -1;
         BindList();

      }

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>DataList Edit Example</h3>

      Click <b>Edit</b> to edit the values of the item.

      <br /><br />

      <asp:DataList id="ItemsList"
           GridLines="Both"
           RepeatColumns="3"
           RepeatDirection="Horizontal"
           CellPadding="3"
           CellSpacing="0"
           OnEditCommand="Edit_Command"
           OnUpdateCommand="Update_Command"
           OnDeleteCommand="Delete_Command"
           OnCancelCommand="Cancel_Command"
           runat="server">

         <HeaderStyle BackColor="#aaaadd">
         </HeaderStyle>

         <AlternatingItemStyle BackColor="Gainsboro">
         </AlternatingItemStyle>

         <EditItemStyle BackColor="yellow">
         </EditItemStyle>

         <HeaderTemplate>

            Items

         </HeaderTemplate>

         <ItemTemplate>

            Item:
            <%# DataBinder.Eval(Container.DataItem, "Item") %> 

            <br />

            Quantity:
            <%# DataBinder.Eval(Container.DataItem, "Qty") %>

            <br />

            Price:
            <%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>

            <br />

            <asp:LinkButton id="EditButton" 
                 Text="Edit" 
                 CommandName="Edit"
                 runat="server"/>

         </ItemTemplate>

         <EditItemTemplate>

            Item:
            <asp:Label id="ItemLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Item") %>' 
                 runat="server"/>

            <br />

            Quantity:
            <asp:TextBox id="QtyTextBox" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Qty") %>' 
                 runat="server"/>

            <br />

            Price:
            <asp:TextBox id="PriceTextBox" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>' 
                 runat="server"/>

            <br />

            <asp:LinkButton id="UpdateButton" 
                 Text="Update" 
                 CommandName="Update" 
                 runat="server"/>

            <asp:LinkButton id="DeleteButton" 
                 Text="Delete" 
                 CommandName="Delete" 
                 runat="server"/>

            <asp:LinkButton id="CancelButton" 
                 Text="Cancel" 
                 CommandName="Cancel" 
                 runat="server"/>

         </EditItemTemplate>

      </asp:DataList>

   </form>

</body>
</html>


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

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>DataList Edit Example</title>
<script runat="server">

      // The Cart and CartView objects temporarily store the data source
      // for the DataList control while the page is being processed.
      DataTable Cart = new DataTable();
      DataView CartView;   

      void Page_Load(Object sender, EventArgs e) 
      {

         // With a database, use an select query to retrieve the data. 
         // Because the data source in this example is an in-memory
         // DataTable, retrieve the data from session state if it exists;
         // otherwise, create the data source.
         GetSource();

         // The DataList control maintains state between posts to the server;
         // it only needs to be bound to a data source the first time the
         // page is loaded or when the data source is updated.
         if (!IsPostBack)
         {

            BindList();

         }

         // Manually register the event-handling methods.
         ItemsList.EditCommand += 
             new DataListCommandEventHandler(this.Edit_Command);
         ItemsList.UpdateCommand += 
             new DataListCommandEventHandler(this.Update_Command);
         ItemsList.DeleteCommand += 
             new DataListCommandEventHandler(this.Delete_Command);
         ItemsList.CancelCommand += 
             new DataListCommandEventHandler(this.Cancel_Command);

      }

      void BindList() 
      {

         // Set the data source and bind to the DataList control.
         ItemsList.DataSource = CartView;
         ItemsList.DataBind();

      }

      void GetSource()
      {

         // For this example, the data source is a DataTable that 
         // is stored in session state. If the data source does not exist,
         // create it; otherwise, load the data.
         if (Session["ShoppingCart"] == null) 
         {     

            // Create the sample data.
            DataRow dr;  

            // Define the columns of the table.
            Cart.Columns.Add(new DataColumn("Qty", typeof(Int32)));
            Cart.Columns.Add(new DataColumn("Item", typeof(String)));
            Cart.Columns.Add(new DataColumn("Price", typeof(Double)));

            // Store the table in session state to persist its values
            // between posts to the server.
            Session["ShoppingCart"] = Cart;

            // Populate the DataTable with sample data.
            for (int i = 1; i <= 9; i++) 
            {
               dr = Cart.NewRow();
               if (i % 2 != 0)
               {
                  dr[0] = 2;
               }
               else
               {
                  dr[0] = 1;
               }
               dr[1] = "Item " + i.ToString();
               dr[2] = (1.23 * (i + 1));
               Cart.Rows.Add(dr);
            }

         } 

         else
         {

            // Retrieve the sample data from session state.
            Cart = (DataTable)Session["ShoppingCart"];

         }         

         // Create a DataView and specify the field to sort by.
         CartView = new DataView(Cart);
         CartView.Sort="Item";

         return;

      }

      void Edit_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Set the EditItemIndex property to the index of the item clicked
         // in the DataList control to enable editing for that item. Be sure
         // to rebind the DataList to the data source to refresh the control.
         ItemsList.EditItemIndex = e.Item.ItemIndex;
         BindList();

      }

      void Cancel_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Set the EditItemIndex property to -1 to exit editing mode. Be sure
         // to rebind the DataList to the data source to refresh the control.
         ItemsList.EditItemIndex = -1;
         BindList();

      }

      void Delete_Command(Object sender, DataListCommandEventArgs e) 
      { 

         // Retrieve the name of the item to remove.
         String item = ((Label)e.Item.FindControl("ItemLabel")).Text;

         // Filter the CartView for the selected item and remove it from
         // the data source.
         CartView.RowFilter = "Item='" + item + "'";
         if (CartView.Count > 0) 
         {
            CartView.Delete(0);
         }
         CartView.RowFilter = "";

         // Set the EditItemIndex property to -1 to exit editing mode. Be sure
         // to rebind the DataList to the data source to refresh the control.
         ItemsList.EditItemIndex = -1;
         BindList();

      }

      void Update_Command(Object sender, DataListCommandEventArgs e) 
      {

         // Retrieve the updated values from the selected item.
         String item = ((Label)e.Item.FindControl("ItemLabel")).Text;
         String qty = ((TextBox)e.Item.FindControl("QtyTextBox")).Text;
         String price = ((TextBox)e.Item.FindControl("PriceTextBox")).Text;

         // With a database, use an update command to update the data.
         // Because the data source in this example is an in-memory 
         // DataTable, delete the old row and replace it with a new one.

         // Filter the CartView for the selected item and remove it from
         // the data source.
         CartView.RowFilter = "Item='" + item + "'";
         if (CartView.Count > 0)
         {
            CartView.Delete(0);
         }
         CartView.RowFilter = "";

         // ***************************************************************
         // Insert data validation code here. Make sure to validate the
         // values entered by the user before converting to the appropriate
         // data types and updating the data source.
         // ***************************************************************

         // Add a new entry to replace the previous item.
         DataRow dr = Cart.NewRow();
         dr[0] = qty;
         dr[1] = item;
         // If necessary, remove the '$' character from the price before
         // converting the price to a Double.
         if(price[0] == '$')
         {
            dr[2] = Convert.ToDouble(price.Substring(1));
         }
         else
         {
            dr[2] = Convert.ToDouble(price);
         }
         Cart.Rows.Add(dr);

         // Set the EditItemIndex property to -1 to exit editing mode. 
         // Be sure to rebind the DataList to the data source to refresh
         // the control.
         ItemsList.EditItemIndex = -1;
         BindList();

      }

   </script>

</head>
<body>

   <form id="form1" runat="server">

      <h3>DataList Edit Example</h3>

      Click <b>Edit</b> to edit the values of the item.

      <br /><br />

      <asp:DataList id="ItemsList"
           GridLines="Both"
           RepeatColumns="3"
           RepeatDirection="Horizontal"
           CellPadding="3"
           CellSpacing="0"
           runat="server">

         <HeaderStyle BackColor="#aaaadd">
         </HeaderStyle>

         <AlternatingItemStyle BackColor="Gainsboro">
         </AlternatingItemStyle>

         <EditItemStyle BackColor="yellow">
         </EditItemStyle>

         <HeaderTemplate>

            Items

         </HeaderTemplate>

         <ItemTemplate>

            Item:
            <%# DataBinder.Eval(Container.DataItem, "Item") %> 

            <br />

            Quantity:
            <%# DataBinder.Eval(Container.DataItem, "Qty") %>

            <br />

            Price:
            <%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>

            <br />

            <asp:LinkButton id="EditButton" 
                 Text="Edit" 
                 CommandName="Edit"
                 runat="server"/>

         </ItemTemplate>

         <EditItemTemplate>

            Item:
            <asp:Label id="ItemLabel" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Item") %>' 
                 runat="server"/>

            <br />

            Quantity:
            <asp:TextBox id="QtyTextBox" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Qty") %>' 
                 runat="server"/>

            <br />

            Price:
            <asp:TextBox id="PriceTextBox" 
                 Text='<%# DataBinder.Eval(Container.DataItem, "Price", "{0:c}") %>' 
                 runat="server"/>

            <br />

            <asp:LinkButton id="UpdateButton" 
                 Text="Update" 
                 CommandName="Update" 
                 runat="server"/>

            <asp:LinkButton id="DeleteButton" 
                 Text="Delete" 
                 CommandName="Delete" 
                 runat="server"/>

            <asp:LinkButton id="CancelButton" 
                 Text="Cancel" 
                 CommandName="Cancel" 
                 runat="server"/>

         </EditItemTemplate>

      </asp:DataList>

   </form>

</body>
</html>

.NET Framework
Verfügbar seit 1.1
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