Dependency Relationship in WPF Gantt

31 Mar 20229 minutes to read

Dependency relationship is the relationship between two tasks. These relationship has been categorized into four types based on the start and finish date of the task. They are:

  • FinishToStart
  • FinishToFinish
  • StartToStart
  • StartToFinish

Finish-to-start—You cannot start a task until the other task is completed.


Finish-to-finish—You cannot finish a task until the other task is completed.


Start-to-start—You cannot start a task until the other task is also started.


Start-to-Finish—You cannot finish a task until another the other task is started.



Property Description Type Data Type Reference links
Predecessor This enables you to set the relationship between the tasks. Object Object NA
GanttTaskRelationship This contains four relationships. They are: * StartToStart * StartToFinish * FinishToFinish * FinishToStart You can assign this to the


to set the relationship between tasks.
Predecessor Enum NA

Specifying the Relationship between Tasks

The following code illustrates how to add the Dependency Relationship between tasks:

  • C#
  • // Adding dependency relationship.
    task[0].ChildCollection[1].Predecessors = new ObservableCollection<Predecessor>(
    task[0].ChildCollection[1].Predecessors.Add(new Predecessor()
                                             GanttTaskIndex = 
                                             GanttTaskRelationship = GanttTaskRelationship.StartToStart
    task[0].ChildCollection[2].Predecessors = new ObservableCollection<Predecessor>();
    task[0].ChildCollection[2].Predecessors.Add(new Predecessor()
                                             GanttTaskIndex = 
                                             GanttTaskRelationship = GanttTaskRelationship.StartToFinish
    task[0].ChildCollection[3].Predecessors = new ObservableCollection<Predecessor>();
    task[0].ChildCollection[3].Predecessors.Add(new Predecessor()
                                             GanttTaskIndex = 
                                             GanttTaskRelationship = GanttTaskRelationship.FinishToFinish

    The following image shows the Dependency Relationship:


    To view samples:

    1. Go to the Syncfusion Essential Studio installed location.
      Location: Installed Location\Syncfusion\Essential Studio\25.2.3\Infrastructure\Launcher\Syncfusion Control Panel
    2. Open the Syncfusion Control Panel in the above location (or) Double click on the Syncfusion Control Panel desktop shortcut menu.
    3. Click Run Samples for WPF under User Interface Edition panel .
    4. Select Gantt.
    5. Expand the Connectors Features item in the Sample Browser.
    6. Choose the Predecessor sample to launch.

    Dynamic Predecessors and Resources

    Essential Gantt provides support for dynamic editing of predecessors in the Grid area. Using this feature, you can dynamically add the predecessor on-demand basis to Gantt. You can add/remove the predecessor in the corresponding cell in the GanttGrid.

    You can add/remove/update the predecessors and resources of tasks at run time. Initially, the Gantt is loaded with the Predecessor/Resource information in the underlying collection and you can update this information if required.

    You can edit the predecessor information from the GanttGrid. For resource, you can edit in the underlying source, Gantt will listen to the change in the underlying source and reflect it in both GanttGrid and GanttChart.

    Predecessor Validation

    There are two predecessor validation modes in Gantt Control.

    • Auto - Successor nodes will adjust its position based on its predecessor nodes automatically.
    • Manual - Successor nodes need to adjust manually with respect to predecessor.


    Property Description Type Data Type Reference links
    ValidationMode This contains two modes.
    • Manual,
    • Auto.
    Default value is Manual.
    DependencyProperty Enum NA

    The following image shows the Predecessor in Manual Mode:

    Predecessors ManualMode

    The following image shows the Predecessor in Auto Mode:

    Predecessors AutoMode

    Editing Predecessors

    While creating a new predecessor in Grid, it should be in the following format:

  • C#
  • {Task ID}{GanttTaskRelationship}

    Here the {GanttTaskRelationship} is any one of the following:

    • SS
    • FS
    • SF
    • FF

    The following are what you should use for different relationships:

    • Use “SS” to define the “StartToStart” relationship
    • Use “FS” to define the “FinishToStart” relationship
    • Use “SF” to define the “StartToFinish” relationship
    • Use “FF” to define the “FinishToFinish” relationship

    If any other data is added, the current editing relationship will be deleted and only the valid predecessors remain for the task.

    Editing Resources

    As of now, resources cannot be edited in Grid. You can update the resource collection in the underlying source whenever you need. Gantt will listen to the changes in the collection and will update the GanttGrid and GanttChart accordingly.

    Use Case Scenario

    This helps to change the dependency relationships and resources of the tasks dynamically.


    Adding Dynamic Predecessors and Resources to an Application

    The dynamic editing of predecessor will be automatically included in the Gantt by default. There is no need to provide any additional data for that. The following codes illustrate this:

  • XAML
  • <Sync:GanttControl ItemsSource="{Binding TaskCollection}" >
            <Sync:TaskAttributeMapping TaskIdMapping="Id"
  • C#
  • //// The following code will illustrate how to dynamically add resource and predecessor in the underlying collection:
    // To Add the Dynamic Predecessors
    this.viewModel.GanttItemSource[0].ChildCollection[2].Predecessors.Add(new Predecessor()
                                                         GanttTaskIndex = 3,
                                                         GanttTaskRelationship = GanttTaskRelationship.StartToFinish
    //To Add the Dynamic Resources   
    this.viewModel.GanttItemSource[0].ChildTask[2].Resource.Add(new Resource { ID = 3, Name = "Resource3" });