How to: Implement Dependency Constraints in the Gantt View

• Jan 23, 2019
• 2 minutes to read

This code snippet illustrates how to apply the AppointmentDependencyType.FinishToStart dependency restrictions on modifications of appointment Appointment.Start and Appointment.End values within the Gantt View.

The SchedulerOptionsCustomization.AllowAppointmentConflicts option of the Scheduler is set to AppointmentConflictsMode.Custom. It allows the SchedulerControl to raise the SchedulerControl.AllowAppointmentConflicts event.

The code within this event handler analyzes all dependencies of the specified (Finish-to-Start) type established with the appointment for which the event is raised. If Start or End properties of the modified appointment do not meet criteria, it is thought that a conflict occurs.

If a conflict occurs, appointment modifications are canceled automatically.

View Example

Form1.cs

private void schedulerControl1_AllowAppointmentConflicts(object sender, AppointmentConflictEventArgs e)
{
    e.Conflicts.Clear();

    AppointmentDependencyBaseCollection depCollectionDep = 
        schedulerStorage1.AppointmentDependencies.Items.GetDependenciesByDependentId(e.Appointment.Id);
    if (depCollectionDep.Count > 0) {
        if (CheckForInvalidDependenciesAsDependent(depCollectionDep, e.AppointmentClone))
            e.Conflicts.Add(e.AppointmentClone);
    }

    AppointmentDependencyBaseCollection depCollectionPar = 
        schedulerStorage1.AppointmentDependencies.Items.GetDependenciesByParentId(e.Appointment.Id);
    if (depCollectionPar.Count > 0) {
        if (CheckForInvalidDependenciesAsParent(depCollectionPar, e.AppointmentClone))
            e.Conflicts.Add(e.AppointmentClone);
    }
}

private bool CheckForInvalidDependenciesAsDependent(AppointmentDependencyBaseCollection depCollection, Appointment apt)
{
    foreach (AppointmentDependency dep in depCollection) {
        if (dep.Type == AppointmentDependencyType.FinishToStart) {
            DateTime checkTime = schedulerStorage1.Appointments.Items.GetAppointmentById(dep.ParentId).End;
            if (apt.Start < checkTime)
                return true;
        }
    }
    return false;
}

private bool CheckForInvalidDependenciesAsParent(AppointmentDependencyBaseCollection depCollection, Appointment apt)
{
    foreach (AppointmentDependency dep in depCollection) {
        if (dep.Type == AppointmentDependencyType.FinishToStart) {
            DateTime checkTime = schedulerStorage1.Appointments.Items.GetAppointmentById(dep.DependentId).Start;
            if (apt.End > checkTime)
                return true;
        }
    }
    return false;
}

Form1.vb

Private Sub schedulerControl1_AllowAppointmentConflicts(ByVal sender As Object, ByVal e As AppointmentConflictEventArgs)
    e.Conflicts.Clear()

    Dim depCollectionDep As AppointmentDependencyBaseCollection = schedulerStorage1.AppointmentDependencies.Items.GetDependenciesByDependentId(e.Appointment.Id)
    If depCollectionDep.Count > 0 Then
        If CheckForInvalidDependenciesAsDependent(depCollectionDep, e.AppointmentClone) Then
            e.Conflicts.Add(e.AppointmentClone)
        End If
    End If

    Dim depCollectionPar As AppointmentDependencyBaseCollection = schedulerStorage1.AppointmentDependencies.Items.GetDependenciesByParentId(e.Appointment.Id)
    If depCollectionPar.Count > 0 Then
        If CheckForInvalidDependenciesAsParent(depCollectionPar, e.AppointmentClone) Then
            e.Conflicts.Add(e.AppointmentClone)
        End If
    End If
End Sub

Private Function CheckForInvalidDependenciesAsDependent(ByVal depCollection As AppointmentDependencyBaseCollection, ByVal apt As Appointment) As Boolean
    For Each dep As AppointmentDependency In depCollection
        If dep.Type = AppointmentDependencyType.FinishToStart Then
            Dim checkTime As DateTime = schedulerStorage1.Appointments.Items.GetAppointmentById(dep.ParentId).End
            If apt.Start < checkTime Then
                Return True
            End If
        End If
    Next dep
    Return False
End Function

Private Function CheckForInvalidDependenciesAsParent(ByVal depCollection As AppointmentDependencyBaseCollection, ByVal apt As Appointment) As Boolean
    For Each dep As AppointmentDependency In depCollection
        If dep.Type = AppointmentDependencyType.FinishToStart Then
            Dim checkTime As DateTime = schedulerStorage1.Appointments.Items.GetAppointmentById(dep.DependentId).Start
            If apt.End > checkTime Then
                Return True
            End If
        End If
    Next dep
    Return False
End Function