如何自定义asp.net下拉列表以支持自定义数据绑定字段
本文关键字:自定义 支持 数据绑定 字段 net asp 下拉列表 | 更新日期: 2023-09-27 18:15:08
是否有办法自定义asp.net下拉列表来支持自定义数据绑定字段。它不应该是控件的自定义属性。它应该能够通过DataBind();
方法与相同的数据源绑定数据。在这个自定义服务器控件中,我试图访问新的自定义字段,并基于该值,我将为数据源的特定行做一些计算。
标准控制代码
<asp:DropDownList runat="server" DataTextField="TextField" DataValueField="ValueField"/>
新的自定义控件应该看起来像这样,
<asp:DropDownList runat="server" DataTextField="TextField" DataValueField="ValueField" DataCustomField="CustomField"/>
你可以这样扩展下拉列表:
public class MyDropDownList : DropDownList
{
public MyDropDownList()
{
}
public string CustomProperty { get; set; }
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
int i = 0;
foreach (var item in this.DataSource as IEnumerable)
{
PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(item);
PropertyDescriptor pd = properties.Find(CustomProperty, true);
this.Items[i].Attributes.Add(CustomProperty, pd.GetValue(item).ToString());
i++;
}
}
}
并在你的标记上使用它,如下所示:
<cc1:MyDropDownList ID="MyDropDownList1" DataTextField="Name" DataValueField="Department" CustomProperty="ImageUrl" runat="server">
</cc1:MyDropDownList>
在我的情况下,我绑定到一个List<Employee>
与一些属性,如Name
, Department
和ImageUrl
。渲染后的下拉菜单如下所示:
<select name="ctl00$MainContent$MyDropDownList1" id="MainContent_MyDropDownList1">
<option selected="selected" value="Human resources" ImageUrl="http://www.freedigitalphotos.net/images/gal_images/av-_146.jpg">Employee 0</option>
<option value="Information Technology" ImageUrl="http://www.freedigitalphotos.net/images/gal_images/av-_314.jpg">Employee 1</option>
<option value="Human resources" ImageUrl="http://www.freedigitalphotos.net/images/gal_images/av-_146.jpg">Employee 2</option>
<option value="Information Technology" ImageUrl="http://www.freedigitalphotos.net/images/gal_images/av-_314.jpg">Employee 3</option>
<option value="Human resources" ImageUrl="http://www.freedigitalphotos.net/images/gal_images/av-_146.jpg">Employee 4</option>
</select>
UPDATE:(对于@emrahozguner,他通过Twitter向我发送了一个关于如何在SelectedIndexChanged
事件上检索CustomProperty
的问题)
public class MyDropDownList : DropDownList
{
public MyDropDownList()
{
}
public string CustomProperty
{
get;
set;
}
public string SelectedCustomProperty
{
get
{
//Use the SelectedIndex to retrieve the right element from ViewState
return ViewState["CustomProperty" + this.SelectedIndex] as string;
}
}
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
int i = 0;
if (this.DataSource != null)
{
foreach (var item in this.DataSource as IEnumerable)
{
PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(item);
PropertyDescriptor pd = properties.Find(CustomProperty, true);
this.Items[i].Attributes.Add(CustomProperty, pd.GetValue(item).ToString());
//We need to save the CustomProperty value on ViewState if we want to be able to retrieve it...
ViewState["CustomProperty" + i] = pd.GetValue(item).ToString();
i++;
}
}
}
}
在SelectedIndexChanged
上访问CustomProperty
:
protected void MyDropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
MyDropDownList l = (sender as MyDropDownList);
if (l != null)
{
string selectedCustomProperty = l.SelectedCustomProperty;
//Do something cool with this selectedCustomProperty
}
}
免责声明:这不是唯一的方法,但这是我能想到的最简单的方法,不需要重写LoadViewState
和SaveViewState
等