基于查询LINQ和ObjectDataSource的DDL DataTextField查询LINQ

Question

I have a problem with this dropdownlist based on an ObjectDataSource

<asp:DropDownList ID="DropDownList1" runat="server" 
                DataSourceID="UserODS" DataTextField="LastName"
                DataValueField="IDUser">
</asp:DropDownList>

<asp:ObjectDataSource ID="UserODS" runat="server" 
                SelectMethod="GetListFullNameUsers" TypeName="DAL.AccessoDB">
</asp:ObjectDataSource>

The method is:

public List<String> GetListFullNameUsers()
{
   using (var context = new UChipDataContext())
   {
      return context.Users
                   .Select(c => new { c.LastName, c.FirstName })
                   .ToList()
                   .Select(c => String.Concat(c.LastName," ", c.FirstName))
                   .ToList(); 
   }
}

But I get this error:

DataBinding: 'System.String' does not contain a property with the name 'LastName'.

How can I solve?

Thanks in advance.

Luigi

Answer 1

OK... the problem here is the following:

Your LINQ query returns a list of plain strings and so your databinding fails because those strings don't have a property called LastName .

One possible solution is to make the anonymous type into a class as shown here returning a strongly typed object with a property called LastName because you have DataTextField="LastName" and so your DropDownList does expect a property called LastName .

Answer 2

Hrm why do you have multiple select / tolists??

Try this:

    return context.Users
                  .Select(c => string.Format("{0} {1}", c.LastName, c.FirstName))
                  .ToList();