How to convert a List into a comma-separated list, using the class's Id property as the value

Question

I have a List collection, and I want to create a comma seperated string using the User.Id property, so:

\"12321,432434,123432452,132         


        

Answer 1

Given this list:

List users = (GetUsers() ?? new List())
   .Where(u => u != null).ToList();

// no more nulls

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.NET 3.5 - String.Join

Join(String, String())

Join(String, String(), Int32, Int32)

Example:

return string.Join(",", users.Select(u => u.Id.ToString()).ToArray());

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.NET 4.0 - String.Join

Join(String, IEnumerable(Of String))

Join(Of T)(String, IEnumerable(Of T))

Join(String, Object()) // really? Just joining "stuff"?

Join(String, String())

Join(String, String(), Int32, Int32)

Example

return string.Join(",", users.Select(u => u.Id));