I have an array of objects similar to this:

 class StateVisitor
 {
     string FirstName { get; set; }
     string LastName { get; set; }
     string StateViseted { get; set; }
 }
    
 StateVisitor[] StateVisitors = {
     new() { FirstName = "Bob", LastName = "Smith", StateViseted = "AL" },
     new() { FirstName = "Bob", LastName = "Smith", StateViseted = "AK" },
     new() { FirstName = "Bob", LastName = "Jones", StateViseted = "AL" },
     new() { FirstName = "Sam", LastName = "Smith", StateViseted = "UT" }
  }

And I want to do something like this:

 class VisitorsWithCombinedStates {
    string FirstName { get; set; }
    string LastName { get; set; }
    string[] StatesVisetedArray { get; set; }
}

 VisitorsWithCombinedStates[] visitorsWithCombinedStates = StateVisitors... /* Linq magic? */

 visitorsWithCombinedStates.ForEach(v 
     => Console.WriteLine($"{v.FirstName} {v.LastName} visited {string.Join(", ",v.StatesVisitedArray)}"));

        // "Bob Smith visited AL, AK"
        // "Bob Jones visited AL"
        // "Sam Smith visited UT"

Is there an easy way, in C# (probably with LINQ) to flatten that first array into the second array, where it makes an array of the states visited?

CodePudding user response：

You want to group your items by a combination of first and last name and project the result of the grouping as just the state visited

var groups = stateVisitors.GroupBy(sv => new
    {
        sv.FirstName,
        sv.LastName,
    },
    sv => sv.StateVisited );

Output:

foreach(var g in groups)
{
    // g.Key.FirstName
    // g.Key.LastName
    // g is IEnumerable<string> of visited states
}

CodePudding user response：

An example, to fill your VisitorsWithCombinedStates class:

VisitorsWithCombinedStates[] visitorsWithCombinedStates = StateVisitors.GroupBy(x => new { x.FirstName, x.LastName},x => x.StateViseted)
.Select(x => new VisitorsWithCombinedStates { FirstName = x.Key.FirstName, LastName = x.Key.LastName, StatesVisetedArray = x.ToArray() }).ToArray();