Passing strongly typed property name as argument

Question

I have a collection of IEnumerable<School> that is being passed to an extension method that populates a DropDownList. I would also like to pass the DataValueField and DataTextField as an argument but I wanted them to be strongly typed.

Basically, I don't want to pass a string for the DataValueField and DataTextField arguments, it's error prone.

public static void populateDropDownList<T>(this DropDownList source,
        IEnumerable<T> dataSource,
        Func<T, string> dataValueField,
        Func<T, string> dataTextField) {
    source.DataValueField = dataValueField; //<-- this is wrong
    source.DataTextField = dataTextField; //<-- this is wrong
    source.DataSource = dataSource;
    source.DataBind();
}

Called like so...

myDropDownList.populateDropDownList(states,
        school => school.stateCode,
        school => school.stateName);

My question is, how can I pass the DataValueField and DataTextField strongly typed as an argument to populateDropDownList?

Answer 1

Based off Jon's answer and this post, it gave me an idea. I passed the DataValueField and DataTextField as Expression<Func<TObject, TProperty>> to my extension method. I created a method that accepts that expression and returns the MemberInfo for that property. Then all I have to call is .Name and I've got my string.

Oh, and I changed the extension method name to populate, it was ugly.

public static void populate<TObject, TProperty>(
        this DropDownList source, 
        IEnumerable<TObject> dataSource, 
        Expression<Func<TObject, TProperty>> dataValueField, 
        Expression<Func<TObject, TProperty>> dataTextField) {
    source.DataValueField = getMemberInfo(dataValueField).Name;
    source.DataTextField = getMemberInfo(dataTextField).Name;
    source.DataSource = dataSource;
    source.DataBind();
}

private static MemberInfo getMemberInfo<TObject, TProperty>(Expression<Func<TObject, TProperty>> expression) {
    var member = expression.Body as MemberExpression;
    if(member != null) {
        return member.Member;
    }
    throw new ArgumentException("Member does not exist.");
}

Called like so...

myDropDownList.populate(states,
    school => school.stateCode,
    school => school.stateName);