Question

I have a combobox that I bind to a list of objects with three properties: int a, int b, and string x. When bound I set DataTextField to x and DataValueField to a. What I want to do is get the value of b in the code-behind after the collection has been bound to the list. I do not want to use ViewState. Can I possibly use reflection? Something like this?

var dataSource = ddlTest.GetDataSource();
var newDataSource = dataSource.GetType().GetProperty("_dataSource", 
    BindingFlags.NonPublic | BindingFlags.Instance);

Answer 1

I’m not sure about this, but you might be able to add b as a custom attribute to the ListItem. Try something like this and see if it works:

var table = new DataTable("TableName"); 

//bind the dropdown to the result set
dropDownList.DataSource = table;
dropDownList.DataBind();

//iterate through the datasource and add custom attributes for each item in the list
table.AsEnumerable().ToList().ForEach(r => 
    dropDownList.Items.FindByValue(r.Field<int>("a").ToString()).Attributes["data-field"] = r.Field<int>("b").ToString());    

If you’d prefer to use a regular foreach loop:

foreach (DataRow row in table.Rows)
{
    var item = dropDownList.FindByValue(row.Field<int>("a").ToString());
    if (item != null)
    {
        item.Attributes["data-value"] = row.Field<int>("b").ToString();
    }
}

If adding custom attributes doesn’t work and you don’t want to use ViewState, you might have to store both a and b in the value field, separated by a delimeter. This can be a pain because you’ll have to parse the items to get the values, but given your requirements that might be the best option if the custom attributes don’t work.