How to use lambda expressions for a function that takes a list of delegates

Question

I'm building an extension method on IList to be able to output the specified properties of any object passed into it as a list, and output it as a CSV string. It looks like:

public static string OutputCSVString<T>(this IList<T> list, List<Func<T, string>> properties)
{
   foreach (var row in list)
   {
     foreach(var item in properties)
     { 
        // Do the output work, including calling item(row).
     }
      // Output new line
   }
 }

Right now, I have to call this method like:

// Assuming I've populated List <Product> ProductList up above...

var columns = new List<Func<Product, string>>();
columns.Add(x => x.Id);
columns.Add(x => x.Name);

string s = ProductList.OutputCSVString(columns);

Is there a better way to pass in my lambda expressions without having to explicitly declare the columns variable, something like:

// This doesn't compile
string s = Products.OutputCSVString(new { p => p.Id , p => p.Name });

Answer 1

Rather than using a List<Func<T, string>> use a Func<T, string>[] and make it a parameter array:

static string OutputCSVString<T>(this IList<T> list,
                                 params Func<T, string>[] properties)

Then you should be able to call:

string s = Products.OutputCSVString(p => p.Id , p => p.Name);

Note that as of C# 6, you should be able to write:

static string OutputCSVString<T>(this IList<T> list,
                                 params IEnumerable<Func<T, string>> properties)

... which would mean you could still use it with a List<Func<T, string>> as well.