MVC – Enhanced DropDownListFor – Part #2

In Part #1, I described a method signature for the Html.DropDownListFor static HtmlHelper method, which was:

@Html.DropDownListFor(m => m.UserId, m => m.UserNames, m => m.Id, m => m.Name)

In this part. I’ll write more about HtmlHelper extension method code to make this work. That’s how you use it in Razor – but what does this method signature look like in the source code? Each of the lambda expressions in the above method signature is an expression which is represented by Expression<Func<T1, T2>> expr. The first parameter will represent the name of the form field rendered, i.e. what the Id and Name values are for the Html <select> element. The second parameter represents the items in the <select> list. The third parameter is the property in the items from the above list which should be rendered in the value attribute of each of the <option> elements of the <select> list. The fourth parameter is the property in the items from the above list which…