LINQ - How to concatenate two fields in a Group By?

Question

I have a ReportStatusEntity class as shown below:

public class ReportsStatusEntity
{
    public string PolicyNumber { get; set; }
    public string ClientName { get; set; }
    public bool HasIndividualBrokers { get; set; }
}

Let's say I have the following list of List<ReportStatusEntity>():

{PolicyNumber = 1, ClientName = "John Doe", HasIndividualBrokers = True},
{PolicyNumber = 1, ClientName = "Sarah Doe", HasIndividualBrokers = True},
{PolicyNumber = 2, ClientName = "Paul Smith", HasIndividualBrokers = False},
{PolicyNumber = 3, ClientName = "Ryan Johnson", HasIndividualBrokers = False}

I want to group by PolicyNumber, then concatenate the ClientNames having same PolicyNumber with '&'.

The grouping should be something like this:

{PolicyNumber = 1, ReportStatusEntity = (PolicyNumber = 1, ClientName = "John Doe & Sarah Doe", HasIndividualBrokers = True)},
{PolicyNumber = 2, ReportStatusEntity = (PolicyNumber = 2, ClientName = "Paul Smith", HasIndividualBrokers = False)},
{PolicyNumber = 3, ReportStatusEntity = (PolicyNumber = 3, ClientName = "Ryan Johnson", HasIndividualBrokers = False)}

How can this be done in C# using LINQ? Thank you.

Answer 1

var list = new List<ReportsStatusEntity>()
{
    new ReportsStatusEntity{PolicyNumber = "1", ClientName = "John Doe", HasIndividualBrokers = true},
    new ReportsStatusEntity{PolicyNumber = "1", ClientName = "Sarah Doe", HasIndividualBrokers = true},
    new ReportsStatusEntity{PolicyNumber = "2", ClientName = "Paul Smith", HasIndividualBrokers = false},
    new ReportsStatusEntity{PolicyNumber = "3", ClientName = "Ryan Johnson", HasIndividualBrokers = false}
};

var results = list.GroupBy(r => r.PolicyNumber)
    .Select(g => new
    {
        PolicyNumber = g.Key,
        // string.Join will not work if its against a database with sql
        ClientNames = string.Join(" & ", g.Select(r => r.ClientName)),
    });

foreach (var result in results)
{
    Console.WriteLine($"Policy {result.PolicyNumber}: {result.ClientNames}");
}

// -- Outputs --
// Policy 1: John Doe & Sarah Doe
// Policy 2: Paul Smith
// Policy 3: Ryan Johnson