如何将自定义属性添加到 asp.net 下拉列表

Question

I am trying to add a country name as country attribute to asp.net dropdown list control but i am not having any luck with it.

ListItem newState;
foreach (DataRow drow in dsDist.Tables(1).Rows)
{
    newState = new ListItem(drow("statename").ToString(), drow("state").ToString());
    newState.Attributes.Add("country", drow("country-name").ToString());
    ddlstates.Items.Add(newState);
}

ddlstates.Items.Insert(0, new ListItem("", ""));
ddlstates.SelectedIndex = 0;

After Page Render;

<select name="ddlStates" id="ddlStates" class="chosen-select-states" data-placeholder="search by state name" style="display: none;">
        <option selected="selected" value=""></option>
        <option value="AK">Alaska</option>
        <option value="AL">Alabama</option>
        <option value="AR">Arkansas</option>
        <option value="AZ">Arizona</option>
</select>

This is what i am expecting;

<option country="usa" value="AK">Alaska</option>
<option country="canada" value="ON">Ontario</option>

Answer 1

Your attributes should be visible on the rendered page with your browser's developer tools. But, attributes won't be posted back and you won't be able to get them back on the SelectedIndexChanged event for example.

You have to create your own custom control derived from DropDownList or to store those attributes elsewhere.

Depending on what you want to do, you could perhaps store a Dictionary<String,String> itemAttributes containing ListItems values and attributes.

This could something as:

Dictionary<string, string> itemAttributes = new Dictionary<string, string>();
            ListItem newState;

            foreach (DataRow drow in dsDist.Tables(1).Rows)
            {
                newState = new ListItem(drow("statename").ToString(), drow("state").ToString());
                //newState.Attributes.Add("country", drow("country-name").ToString());

                ddlstates.Items.Add(newState);
                itemAttributes.Add(drow("state"), drow("country-name"));
            }

            ddlstates.Items.Insert(0, new ListItem("", ""));
            ddlstates.SelectedIndex = 0;

            Session["Attributes"] = itemAttributes;
            ViewState["Attributes"] = itemAttributes;

Beware of the size of the session or viewstate if you use this method.