ASP：列表框 - 回發沒有選定的項目？

我有以下的標記：ASP：列表框 - 回發沒有選定的項目？

<tr> 
    <td valign="top" align="left"> 
     <asp:Label ID="Label1" runat="server" Text="Available Roles" /> 
     <br /> 
     <asp:ListBox ID="availableRolesListBox" runat="server" SelectionMode="Multiple" Width="100px" Rows="10" AutoPostBack="false" /> 
    </td> 
    <td valign="top" align="center"> 
     &nbsp; 
     <br /> 
     <asp:Button ID="addToRole" runat="server" Text="--->" OnClick="addToRole_Click" /> 
     <br /> 
     <asp:Button ID="removeFromRole" runat="server" Text="<---" OnClick="removeFromRole_Click" /> 
    </td> 
    <td valign="top" align="left"> 
     <asp:Label ID="Label2" runat="server" Text="User In Roles" /> 
     <br /> 
     <asp:ListBox ID="userInRolesListBox" runat="server" SelectionMode="Multiple" Width="100px" Rows="10" AutoPostBack="false" /> 
    </td> 
</tr>

而在後臺代碼如下：

protected void addToRole_Click(object sender, EventArgs e) 
{ 
    // Add user to the selected role... 
    foreach (ListItem myItem in availableRolesListBox.Items) 
    { 
     if (myItem.Selected) 
     { 
      Roles.AddUserToRole(userListBox.SelectedItem.Value, myItem.Text); 
     } 
    } 

    Refresh(); 
}

當我步入代碼隱藏絕對沒有項目被選中！我忘了什麼？

來源

2009-08-10 Keith Barrows