c# AppendDataBoundItems =“True"属性允许在列表框中重复

我有一个Listbox在detailsview与我自己的selectedvalue属性。

当我设置Appenddatabounditems="true"时，Listbox的值被复制，否则，当我设置"AppendDatabounditems="false"时，Listbox的selectedvalue不工作。

请告诉我，如何避免在列表框重复。

我的代码片段如下:

[ASPX页面]

<asp:DetailsView ID="dvProfile" runat="server" AutoGenerateRows="False" DataSourceID="odsProfileData">
        <Fields>
            <asp:BoundField DataField="FullName" HeaderText="Full Name" HeaderStyle-Width="100px" />
            <asp:TemplateField HeaderText="Products">
                <ItemTemplate>
                    <iac:MyMultiSelectionDropDown ID="ListBox1" OnDataBound="Databound" runat="server"
                        DataSourceID="odsProducts" DataTextField="FullName" DataValueField="ID" AppendDataBoundItems="true"
                        SelectionMode="Multiple" SelectedValuesCSV='<%# Bind("Products") %>'>
                    </iac:MyMultiSelectionDropDown>
                </ItemTemplate>
                <EditItemTemplate>
                    <iac:MyMultiSelectionDropDown ID="ListBox1" OnDataBound="Databound" runat="server"
                        DataSourceID="odsProducts" DataTextField="FullName" DataValueField="ID" AppendDataBoundItems="true"
                        SelectionMode="Multiple" SelectedValuesCSV='<%# Bind("Products") %>'>
                    </iac:MyMultiSelectionDropDown>
                </EditItemTemplate>
            </asp:TemplateField>
            <asp:CommandField ButtonType="button" ShowEditButton="true" EditText="Edit User Profile" />
        </Fields>
    </asp:DetailsView>

<asp:ObjectDataSource ID="odsProfileData" runat="server" SelectMethod="GetProfileData"
        TypeName="MultiSelectionTest.App_Code.TestData" />
    <asp:ObjectDataSource ID="odsProducts" runat="server" SelectMethod="GetProducts"
        TypeName="MultiSelectionTest.App_Code.TestData" />

[TestData.CS]

//Using this class file i filled the ListBox.
 public class TestData
    {
        public List<ProfileData> GetProfileData()
        {
            List<ProfileData> ret = new List<ProfileData>();
            ret.Add(new ProfileData("Test1", "1,2"));
            return ret;
        }
        public List<Product> GetProducts()
        {
            List<Product> ret = new List<Product>();
            ret.Add(new Product(1, "Product1"));
            ret.Add(new Product(2, "Product2"));
            ret.Add(new Product(3, "Product3"));
            ret.Add(new Product(4, "Product4"));
            return ret;
        }
        public class ProfileData
        {
            public ProfileData(string fullName, string products)
            {
                FullName = fullName;
                Products = products;
            }
            public string FullName { get; set; }
            public string Products { get; set; }
        }
        public class Product
        {
            public Product(int id, string fullName)
            {
                ID = id;
                FullName = fullName;
            }
            public int ID { get; set; }
            public string FullName { get; set; }
        }
    }

[MyMultiselectionDropDown.cs]

 public string SelectedValuesCSV
        {
            get
            {
                string ret = string.Empty;
                foreach (System.Web.UI.WebControls.ListItem li in this.Items)
                {
                    if (li.Selected)
                    {
                        ret += "," + li.Value.ToString();
                    }
                }
                return ret.TrimStart(',');
            }
            set
            {
                if (!_noUpdate)
                {
                    _noUpdate = true;
                    this.DataBind();
                }
                _noUpdate = false;
                IdContainer values = new IdContainer(value);
                foreach (string val in values)
                {
                    System.Web.UI.WebControls.ListItem li = this.Items.FindByValue(val);
                    if (li != null)
                        li.Selected = true;
                }
                //MultiSelectionTest.App_Code.TestData nn = new TestData();
                //object bb = nn.GetProfileData();
            }
        }

使用这个类文件，我得到SelectedValues。

请告诉我。