public partial class Shifts
    {
        public int empId { get; set; }
        public int Id { get; set; }
        public int day { get; set; }
        public System.DateTime start { get; set; }
        public System.DateTime end { get; set; }
        public int location { get; set; }
    
        public virtual employee employee { get; set; }
    }

    public partial class location
    {
        public location()
        {
            this.Shifts = new HashSet<Shifts>();
        }
    
        public int Id { get; set; }
        public string name { get; set; }
   
        public virtual ICollection<Shifts> Shifts { get; set; }

    }

public partial class employee
    {
        public employee()
        {
            this.aktiveSchichten = new HashSet<Shifts>();
        }
    
        public int Id { get; set; }
        public string firstName { get; set; }
        public string lastName { get; set; }

        public virtual ICollection<aktiveSchichten> aktiveSchichten { get; set; }
    }

 var mitarbeiter = db.employee;
            var schichten = db.Shifts.Where(a => a.location == (int)radMultiColumnComboBox2.SelectedValue);
            foreach (var schicht in schichten)
            {
                radScheduler1.Appointments.BeginUpdate();
                int count = 1;
                foreach (var ma in mitarbeiter)
                {
                    this.radScheduler1.Resources.Add(new Resource(count++, ma.firstName + ma.lastName));
                }
                DateTime start = ?;
                DateTime end = ?;
                Appointment appointment1 = new Appointment(start, end, schicht.employee.firstName + schicht.employee.firstName, "test");
                appointment1.BackgroundId = (int)AppointmentBackground.Anniversary;
                appointment1.StatusId = (int)AppointmentStatus.Unavailable;
                radScheduler1.Appointments.Add(appointment1);
                radScheduler1.Appointments.EndUpdate();
           }

 private void RadGridView1_RowFormatting(object sender, RowFormattingEventArgs e)
        {
            try
            {
                if ((string)e.RowElement.RowInfo.Tag == "new row")
                {
                    e.RowElement.DrawFill = true;
                    e.RowElement.BackColor = System.Drawing.Color.LightCyan;
                    e.RowElement.ForeColor = System.Drawing.Color.Black;
                    e.RowElement.Text = "New";
                    e.RowElement.TextAlignment = System.Drawing.ContentAlignment.TopLeft;
                }
                else if (e.RowElement is GridTableHeaderRowElement)
                {
                    e.RowElement.DrawFill = true;
                    e.RowElement.BackColor = System.Drawing.Color.Navy;
                    e.RowElement.NumberOfColors = 1;
                    e.RowElement.ForeColor = System.Drawing.Color.White;
                    e.RowElement.Text = "";
                }
                else
                {
                    e.RowElement.ResetValue(LightVisualElement.DrawFillProperty, Telerik.WinControls.ValueResetFlags.Local);
                    e.RowElement.ResetValue(LightVisualElement.BackColorProperty, Telerik.WinControls.ValueResetFlags.Local);
                    e.RowElement.ResetValue(LightVisualElement.NumberOfColorsProperty, Telerik.WinControls.ValueResetFlags.Local);
                    e.RowElement.ResetValue(LightVisualElement.ForeColorProperty, Telerik.WinControls.ValueResetFlags.Local);
                    e.RowElement.Text = "";
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show($"Uncaught error in {System.Reflection.MethodBase.GetCurrentMethod().Name}: {ex.Message}");
            }
        }

 public partial class mainForm : Form
    {

        public static OleDbConnection con3 = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source = " + Application.StartupPath + "\\parts.accdb");
        public static DataTable dt = new DataTable();
        public OleDbDataAdapter adapter;
        public OleDbCommandBuilder commandbuider;
        public mainForm()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            string SQL = "SELECT * from supplier";
            adapter = new OleDbDataAdapter(SQL, con3);
            commandbuider = new OleDbCommandBuilder(adapter);

            adapter.Fill(dt);

            PartsGrid.DataSource = dt;

            PartsGrid.RowsChanged  += new GridViewCollectionChangedEventHandler(PartsGrid_Update);

        }

        private void PartsGrid_Update(object sender, GridViewCollectionChangedEventArgs e)
        {
            if (adapter.Update(dt) > 0)
            {
                MessageBox.Show("done");
            }
        }
    }

Public Class RadForm5
    Private Sub RadForm5_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim listTest As New List(Of TestDate)
        listTest.Add(New TestDate With {.Name = "John", .DateStart = New Date(2022, 5, 1)})
        listTest.Add(New TestDate With {.Name = "Arya", .DateStart = New Date(2022, 5, 2)})
        listTest.Add(New TestDate With {.Name = "Brandon", .DateStart = New Date(2022, 5, 3)})
        listTest.Add(New TestDate With {.Name = "Catelyn", .DateStart = New Date(2022, 5, 4)})

        For Each col In RadGridView1.Columns
            If col.Name = "colDate" Then
                col.FieldName = "DateStart"
                Dim colDate As GridViewDateTimeColumn = TryCast(col, GridViewDateTimeColumn)
                colDate.Format = DateTimePickerFormat.Short
            End If
        Next

        RadGridView1.DataSource = listTest
    End Sub
End Class

Public Class TestDate
    Public Property Name As String
    Public Property DateStart As Date
    Public Sub New()

    End Sub
End Class

   Public ReadOnly Property DateStartStr As String
        Get
            Return DateStart.ToShortDateString
        End Get
    End Property

col.FieldName = "DateStartStr"