C#

<pre>namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Customer> CustomerList = new List<Customer>();
            CustomerList.Add(new Customer { ID = 1, Name = "One", GroupID = 1 });
            CustomerList.Add(new Customer { ID = 2, Name = "Two", GroupID = 1 });
            CustomerList.Add(new Customer { ID = 3, Name = "Three", GroupID = 2 });
            CustomerList.Add(new Customer { ID = 4, Name = "Four", GroupID = 1 });
            CustomerList.Add(new Customer { ID = 5, Name = "Five", GroupID = 3 });
            CustomerList.Add(new Customer { ID = 6, Name = "Six", GroupID = 3 });

            IEnumerable<CustomerGrouping> CustomerGroupings = CustomerList.GroupBy(u => u.GroupID)
                                                  .Select(group => new CustomerGrouping { GroupID = group.Key, Customers = group.ToList() })
                                                  .ToList();
        }
    }

    public class Customer
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public int GroupID { get; set; }
    }

    public class CustomerGrouping
    {
        public int GroupID { get; set; }
        public IEnumerable<Customer> Customers { get; set; }
    }

mjeeves wrote:

s this the best method / approach

<pre>namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            List<SignInReport> SignInReports = new List<SignInReport>();
            SignInReports.Add(new SignInReport { UserName = "Bob", EventName = "SignIn", EventTime = new DateTime(2020,1,18,6,0,0) });
            SignInReports.Add(new SignInReport { UserName = "Bob", EventName = "SignOut", EventTime = new DateTime(2020, 1, 18, 10, 0, 0) });
            SignInReports.Add(new SignInReport { UserName = "Bob", EventName = "SignIn", EventTime = new DateTime(2020, 1, 18, 11, 30, 0) });
            SignInReports.Add(new SignInReport { UserName = "Bob", EventName = "SignOut", EventTime = new DateTime(2020, 1, 18, 16, 30, 0) });
            SignInReports.Add(new SignInReport { UserName = "Charlie", EventName = "SignIn", EventTime = new DateTime(2020, 1, 18, 6, 0, 0) });
            SignInReports.Add(new SignInReport { UserName = "Charlie", EventName = "SignOut", EventTime = new DateTime(2020, 1, 18, 15, 30, 0) });
            SignInReports.Add(new SignInReport { UserName = "Charlie", EventName = "SignIn", EventTime = new DateTime(2020, 1, 19, 6, 30, 0) });
            SignInReports.Add(new SignInReport { UserName = "Charlie", EventName = "SignOut", EventTime = new DateTime(2020, 1, 19, 17, 45, 0) });

            IEnumerable<SignInReportGrouping> SignInData = SignInReports.GroupBy(u => u.UserName)
                                                  .Select(group => new SignInReportGrouping {   UserName = group.Key, 
                                                                                                SignInReports = group.ToList() })
                                                  .ToList();
        }
    }

    public class SignInReport
    {
        public string UserName { get; set; }
        public string EventName { get; set; }
        public DateTime EventTime { get; set; }
    }

    public class SignInReportGrouping
    {
        public string UserName { get; set; }
        public IEnumerable<SignInReportDay> SignInReportDay { get; set; }
    }

    public class SignInReportDay
    {
        public IEnumerable<SignInReport> SignInReports { get; set; }
    }
}

IEnumerable<SignInReportGrouping> SignInData = SignInReports
    .GroupBy(u => u.UserName)
    .Select(user => new SignInReportGrouping
    {
        UserName = user.Key,
        SignInReportDay = user
            .GroupBy(u => u.EventTime.Date)
            .Select(day => new SignInReportDay
            {
                Day = day.Key,
                SignInReports = day.ToList(),
            })
            .ToList(),
    })
    .ToList();

public class SignInReportDay
{
    public DateTime Day { get; set; }
    public IEnumerable<SignInReport> SignInReports { get; set; }
}

.GroupBy(u => DbFunctions.TruncateTime(u.EventTime))

Packaging Fonts with Applications - WPF .NET Framework | Microsoft Docs[^]:

In order to reference font resource items from code, you must supply a two-part font resource reference: the base uniform resource identifier (URI); and the font location reference.

<Window.Resources>
    <Style x:Key="Foo">
        <Setter Property="TextElement.FontFamily" Value="pack://application:,,,/Main;component/Fonts/#MyFont" />
    </Style>
    <Style x:Key="Bar">
        <Setter Property="TextElement.FontFamily" Value="./Fonts/#MyFont" />
    </Style>
    <FontFamily x:Key="Baz">./Fonts/#MyFont</FontFamily>
</Window.Resources>

<StackPanel Orientation="Vertical">
     <TextBlock Text="" Style="{StaticResource Foo}" />
     <TextBlock Text="" Style="{StaticResource Bar}" />
     <TextBlock Text="" FontFamily="{StaticResource Baz}" />
     <TextBlock FontFamily="Segoe MDL2 Assets" Text="" />
     <TextBlock x:Name="txt1" />
     <TextBlock x:Name="txt2" />
 </StackPanel>

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    txt1.FontFamily = new FontFamily("pack://application:,,,/Main;component/Fonts/#MyFont");
    txt1.FontFamily = new FontFamily(new Uri("pack://application:,,,/Fonts/"), "./#MyFont");
    txt1.FontFamily = new FontFamily("MyFont");
    txt1.Text = "\xe905";
}

Quote:

You can tell the debugger which exceptions or sets of exceptions to break on, and at which point you want the debugger to break (that is, pause in the debugger)

OriginalGriff wrote:

an exception occurs that you aren't handling (and that is in the "break on this exception" list your project has set)

myDataTable = new DataTable();
myDataTable.Columns.Add("C1");
myDataTable.Columns.Add("C2");
myDataTable.Columns[0].Caption = "A new caption";
myDataGridView.Columns.Clear();
myDataGridView.DataSource = myDataTable;
for (int i = 0; i < myDataTable.Columns.Count; i++)
    {
    myDataGridView.Columns[i].HeaderText = myDataTable.Columns[i].Caption;
    }

<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />