ListView.SelectedValue Proprietà
Definizione
Importante
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Ottiene il valore della chiave di dati dell'elemento selezionato in un controllo ListView.
public:
property System::Object ^ SelectedValue { System::Object ^ get(); };[System.ComponentModel.Browsable(false)]
public object SelectedValue { get; }[<System.ComponentModel.Browsable(false)>]
member this.SelectedValue : objPublic ReadOnly Property SelectedValue As ObjectValore della proprietà
Il valore della chiave di dati dell'elemento selezionato in un controllo ListView.
- Attributi
Esempio
Nell'esempio seguente viene illustrato come usare il primo campo chiave come parametro in uno scenario master/dettaglio. Quando un elemento viene selezionato nel ListView controllo, la SelectedValue proprietà viene usata come oggetto PropertyName per l'oggetto ControlParameter . Questo oggetto parametro viene usato a sua volta dal SqlDataSource controllo a cui è associato il secondo ListView controllo.
<%@ Page language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void CategoriesListView_OnItemDeleting(object sender, ListViewDeleteEventArgs e)
{
if (SubCategoriesGridView.Rows.Count > 0)
{
MessageLabel.Text = "You cannot delete a category that has sub-categories.";
e.Cancel = true;
}
}
protected void Page_Load()
{
MessageLabel.Text = String.Empty;
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Subcategories List</title>
</head>
<body>
<form id="form1" runat="server">
<b>Categories</b>
<br />
<asp:Label ForeColor="Red" runat="server" ID="MessageLabel" /><br />
<asp:ListView runat="server"
ID="CategoriesListView"
OnItemDeleting="CategoriesListView_OnItemDeleting"
DataSourceID="CategoriesDataSource"
DataKeyNames="ProductCategoryID">
<LayoutTemplate>
<table runat="server" id="tblCategories"
cellspacing="0" cellpadding="1" width="440px" border="1">
<tr id="itemPlaceholder" runat="server"></tr>
</table>
</LayoutTemplate>
<ItemTemplate>
<tr runat="server">
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td style="width:40px">
<asp:LinkButton runat="server" ID="SelectCategoryButton"
Text="Select" CommandName="Select" />
</td>
</tr>
</ItemTemplate>
<SelectedItemTemplate>
<tr runat="server" style="background-color:#90EE90">
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td style="width:40px">
<asp:LinkButton runat="server" ID="SelectCategoryButton"
Text="Delete" CommandName="Delete" />
</td>
</tr>
</SelectedItemTemplate>
</asp:ListView>
<br />
<b>Subcategories</b>
<asp:GridView runat="server" ID="SubCategoriesGridView" Width="300px"
DataSourceID="SubCategoriesDataSource" DataKeyNames="ProductSubcategoryID"
AutoGenerateColumns="True" />
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the AdventureWorks sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:SqlDataSource ID="CategoriesDataSource" runat="server"
ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
SelectCommand="SELECT [ProductCategoryID], [Name]
FROM Production.ProductCategory">
</asp:SqlDataSource>
<asp:SqlDataSource ID="SubCategoriesDataSource" runat="server"
ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
SelectCommand="SELECT [ProductSubcategoryID], [Name]
FROM Production.ProductSubcategory
WHERE ProductCategoryID = @ProductCategoryID
ORDER BY [Name]">
<SelectParameters>
<asp:ControlParameter Name="ProductCategoryID" DefaultValue="0"
ControlID="CategoriesListView" PropertyName="SelectedValue" />
</SelectParameters>
</asp:SqlDataSource>
</form>
</body>
</html>
<%@ Page language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub CategoriesListView_OnItemDeleting(sender As Object, e As ListViewDeleteEventArgs)
If SubCategoriesGridView.Rows.Count > 0 Then
MessageLabel.Text = "You cannot delete a category that has sub-categories."
e.Cancel = True
End If
End Sub
Protected Sub Page_Load()
MessageLabel.Text = String.Empty
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>Subcategories List</title>
</head>
<body>
<form id="form1" runat="server">
<b>Categories</b>
<br />
<asp:Label ForeColor="Red" runat="server" ID="MessageLabel" /><br />
<asp:ListView runat="server"
ID="CategoriesListView"
OnItemDeleting="CategoriesListView_OnItemDeleting"
DataSourceID="CategoriesDataSource"
DataKeyNames="ProductCategoryID">
<LayoutTemplate>
<table runat="server" id="tblCategories"
cellspacing="0" cellpadding="1" width="440px" border="1">
<tr id="itemPlaceholder" runat="server"></tr>
</table>
</LayoutTemplate>
<ItemTemplate>
<tr runat="server">
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td style="width:40px">
<asp:LinkButton runat="server" ID="SelectCategoryButton"
Text="Select" CommandName="Select" />
</td>
</tr>
</ItemTemplate>
<SelectedItemTemplate>
<tr runat="server" style="background-color:#90EE90">
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td style="width:40px">
<asp:LinkButton runat="server" ID="SelectCategoryButton"
Text="Delete" CommandName="Delete" />
</td>
</tr>
</SelectedItemTemplate>
</asp:ListView>
<br />
<b>Subcategories</b>
<asp:GridView runat="server" ID="SubCategoriesGridView" Width="300px"
DataSourceID="SubCategoriesDataSource" DataKeyNames="ProductSubcategoryID"
AutoGenerateColumns="True" />
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the AdventureWorks sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:SqlDataSource ID="CategoriesDataSource" runat="server"
ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
SelectCommand="SELECT [ProductCategoryID], [Name]
FROM Production.ProductCategory">
</asp:SqlDataSource>
<asp:SqlDataSource ID="SubCategoriesDataSource" runat="server"
ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
SelectCommand="SELECT [ProductSubcategoryID], [Name]
FROM Production.ProductSubcategory
WHERE ProductCategoryID = @ProductCategoryID
ORDER BY [Name]">
<SelectParameters>
<asp:ControlParameter Name="ProductCategoryID" DefaultValue="0"
ControlID="CategoriesListView" PropertyName="SelectedValue" />
</SelectParameters>
</asp:SqlDataSource>
</form>
</body>
</html>
Nell'esempio seguente viene illustrato come usare la SelectedValue proprietà per determinare il valore del campo chiave.
<%@ Page language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
protected void DepartmentsListView_SelectedIndexChanged(object sender, EventArgs e)
{
MessageLabel.Text = "The key value is " +
DepartmentsListView.SelectedValue.ToString() + ".";
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>ListView SelectedValue Example</title>
<style type="text/css">
.header
{
border: 1px solid #008080;
background-color: #008080;
color: White;
}
.item td { border: 1px solid #008080; }
.selection td
{
border: 1px solid #008080;
background-color: #7FFF00;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<h3>ListView SelectedValue Example</h3>
<asp:ListView runat="server"
ID="DepartmentsListView"
DataSourceID="DepartmentDataSource"
DataKeyNames="DepartmentID"
OnSelectedIndexChanged="DepartmentsListView_SelectedIndexChanged">
<LayoutTemplate>
<b>Department List</b>
<br />
<table width="500px" runat="server" id="tblDepartments">
<tr class="header" runat="server">
<th runat="server"> </th>
<th runat="server">Department Name</th>
<th runat="server">Group Name</th>
</tr>
<tr runat="server" id="itemPlaceholder" />
</table>
</LayoutTemplate>
<ItemTemplate>
<tr class="item" runat="server">
<td>
<asp:LinkButton runat="server"
ID="SelectButton"
Text="Select"
CommandName="Select" />
</td>
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td>
<asp:Label runat="server" ID="GroupNameLabel" Text='<%#Eval("GroupName") %>' />
</td>
</tr>
</ItemTemplate>
<SelectedItemTemplate>
<tr class="selection" runat="server">
<td> </td>
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td>
<asp:Label runat="server" ID="GroupNameLabel" Text='<%#Eval("GroupName") %>' />
</td>
</tr>
</SelectedItemTemplate>
</asp:ListView>
<br/>
<asp:Label ID="MessageLabel"
ForeColor="Red"
runat="server"/>
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the AdventureWorks sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:SqlDataSource ID="DepartmentDataSource" runat="server"
ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
SelectCommand="SELECT DepartmentID, Name, GroupName
FROM HumanResources.Department">
</asp:SqlDataSource>
</form>
</body>
</html>
<%@ Page language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
Protected Sub DepartmentsListView_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
MessageLabel.Text = "The key value is " & _
DepartmentsListView.SelectedValue.ToString() & "."
End Sub
</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
<title>ListView SelectedValue Example</title>
<style type="text/css">
.header
{
border: 1px solid #008080;
background-color: #008080;
color: White;
}
.item td { border: 1px solid #008080; }
.selection td
{
border: 1px solid #008080;
background-color: #7FFF00;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<h3>ListView SelectedValue Example</h3>
<asp:ListView runat="server"
ID="DepartmentsListView"
DataSourceID="DepartmentDataSource"
DataKeyNames="DepartmentID"
OnSelectedIndexChanged="DepartmentsListView_SelectedIndexChanged">
<LayoutTemplate>
<b>Department List</b>
<br />
<table width="500px" runat="server" id="tblDepartments">
<tr class="header" runat="server">
<th runat="server"> </th>
<th runat="server">Department Name</th>
<th runat="server">Group Name</th>
</tr>
<tr runat="server" id="itemPlaceholder" />
</table>
</LayoutTemplate>
<ItemTemplate>
<tr class="item" runat="server">
<td>
<asp:LinkButton runat="server"
ID="SelectButton"
Text="Select"
CommandName="Select" />
</td>
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td>
<asp:Label runat="server" ID="GroupNameLabel" Text='<%#Eval("GroupName") %>' />
</td>
</tr>
</ItemTemplate>
<SelectedItemTemplate>
<tr class="selection" runat="server">
<td> </td>
<td>
<asp:Label runat="server" ID="NameLabel" Text='<%#Eval("Name") %>' />
</td>
<td>
<asp:Label runat="server" ID="GroupNameLabel" Text='<%#Eval("GroupName") %>' />
</td>
</tr>
</SelectedItemTemplate>
</asp:ListView>
<br/>
<asp:Label ID="MessageLabel"
ForeColor="Red"
runat="server"/>
<!-- This example uses Microsoft SQL Server and connects -->
<!-- to the AdventureWorks sample database. Use an ASP.NET -->
<!-- expression to retrieve the connection string value -->
<!-- from the Web.config file. -->
<asp:SqlDataSource ID="DepartmentDataSource" runat="server"
ConnectionString="<%$ ConnectionStrings:AdventureWorks_DataConnectionString %>"
SelectCommand="SELECT DepartmentID, Name, GroupName
FROM HumanResources.Department">
</asp:SqlDataSource>
</form>
</body>
</html>
Commenti
La DataKeyNames proprietà può essere impostata su un elenco delimitato da virgole di nomi di campo che rappresentano la chiave primaria dell'origine dati. Se è impostato, il ListView controllo crea automaticamente un DataKey oggetto per ogni elemento del controllo usando il valore o i valori del campo o dei campi specificati. Gli DataKey oggetti vengono quindi aggiunti all'insieme del DataKeys controllo.
In genere, la DataKeys proprietà viene usata per ottenere l'oggetto DataKey per un elemento di dati specifico nel ListView controllo. Tuttavia, se si vuole ottenere solo l'oggetto DataKey dell'elemento attualmente selezionato, è possibile usare la SelectedDataKey proprietà come collegamento. È anche possibile determinare direttamente il valore della chiave dati del primo campo chiave dell'elemento selezionato usando la SelectedValue proprietà .
Se si crea un oggetto e si vuole accedere a un ControlParameter campo chiave diverso dal primo campo, usare la SelectedDataKey proprietà . Per un esempio, vedere la SelectedDataKey proprietà.