Angular Gantt - validation
Configures validation properties.
jQuery
$(function() {
    $("#gantt").dxGantt({
        validation: {
            autoUpdateParentTasks: true,
            validateDependencies: true
        },
        // ...
    });
});Angular
<dx-gantt ... >
    <dxo-validation
        [autoUpdateParentTasks]="true" 
        [validateDependencies]="true">
    </dxo-validation>
    <!-- ... -->
</dx-gantt>
import { Component } from '@angular/core';
@Component({
    selector: 'app-root',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.css']
})
export class AppComponent {
    // ...      
}
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import { DxGanttModule } from 'devextreme-angular';
@NgModule({
    imports: [
        BrowserModule,
        DxGanttModule
    ],        
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }Vue
<template>
    <DxGantt ... >
        <DxValidation
            :auto-update-parent-tasks="true"
            :validate-dependencies="true" 
         />
        <!-- ... -->
    </DxGantt>
</template>
<script>
    import 'devextreme/dist/css/dx.light.css';
    import 'devexpress-gantt/dist/dx-gantt.css'; 
    import { 
        DxGantt, 
        DxValidation, 
        // ... 
    } from 'devextreme-vue/gantt';
    export default {
        components: { 
            DxGantt, 
            DxValidation, 
            // ... 
        }
    };
</script>React
import React from 'react';
import 'devextreme/dist/css/dx.light.css';
import 'devexpress-gantt/dist/dx-gantt.css'; 
import Gantt, { 
    Validation, 
    // ... 
} from 'devextreme-react/gantt';
const App = () => {
    return (
        <Gantt ... >
            <Validation
                autoUpdateParentTasks={true}
                validateDependencies={true} />
            {/* ... */}
        </Gantt>
    );
};
export default App;ASP.NET Core Controls
@(Html.DevExtreme().Gantt()
    .Validation(e => {
        e.AutoUpdateParentTasks(true)
        e.ValidateDependencies(true)
    })
    // ...
)ASP.NET MVC Controls
@(Html.DevExtreme().Gantt()
    .Validation(e => {
        e.AutoUpdateParentTasks(true)
        e.ValidateDependencies(true)
    })
    // ...
)autoUpdateParentTasks
Specifies whether to recalculate the parent task's duration and progress when its child tasks are modified.
The Gantt uses the following rules to determine whether to update a parent task when its subtask is modified.
- A parent task's duration equals a summary duration of its child tasks.
- A parent task and its first child starts at the same time.
- A parent task and its last child ends at the same time.
- A parent task's progress is a summary progress of its child tasks.

enablePredecessorGap
Specifies whether users can move or resize a predecessor to change a gap before a successor according to the dependency rules.
The Gantt component allows users to change the gap between tasks only if they move/resize a successor task. Note that users can use only a successor to create the gap between tasks.
The following image illustrates that the Gantt does not resize the gap between tasks when users move the predecessor:
 
 
The enablePredecessorGap option allows users to increase/decrease the gap between the tasks with a predecessor. The Gantt component validates these changes and shifts the successor task to comply with the dependency rules if they are violated.

jQuery
$(function() {
    $("#gantt").dxGantt({
        validation: {
            validateDependencies: true,
            enablePredecessorGap: true
        },
        // ...
    });
});Angular
<dx-gantt ... >
    <dxo-validation
        [enablePredecessorGap]="true" 
        [validateDependencies]="true">
    </dxo-validation>
    <!-- ... -->
</dx-gantt>
import { Component } from '@angular/core';
@Component({
    selector: 'app-root',
    templateUrl: './app.component.html',
    styleUrls: ['./app.component.css']
})
export class AppComponent {
    // ...      
}
import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import { DxGanttModule } from 'devextreme-angular';
@NgModule({
    imports: [
        BrowserModule,
        DxGanttModule
    ],        
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }Vue
<template>
    <DxGantt ... >
        <DxValidation
            :enable-predecessor-gap="true"
            :validate-dependencies="true" 
         />
        <!-- ... -->
    </DxGantt>
</template>
<script>
    import 'devextreme/dist/css/dx.light.css';
    import 'devexpress-gantt/dist/dx-gantt.css'; 
    import { 
        DxGantt, 
        DxValidation, 
        // ... 
    } from 'devextreme-vue/gantt';
    export default {
        components: { 
            DxGantt, 
            DxValidation, 
            // ... 
        }
    };
</script>React
import React from 'react';
import 'devextreme/dist/css/dx.light.css';
import 'devexpress-gantt/dist/dx-gantt.css'; 
import Gantt, { 
    Validation, 
    // ... 
} from 'devextreme-react/gantt';
const App = () => {
    return (
        <Gantt ... >
            <Validation
                enablePredecessorGap={true}
                validateDependencies={true} />
            {/* ... */}
        </Gantt>
    );
};
export default App;ASP.NET Core Controls
@(Html.DevExtreme().Gantt()
    .Validation(e => {
        e.EnablePredecessorGap(true)
        e.ValidateDependencies(true)
    })
    // ...
)ASP.NET MVC Controls
@(Html.DevExtreme().Gantt()
    .Validation(e => {
        e.EnablePredecessorGap(true)
        e.ValidateDependencies(true)
    })
    // ...
)validateDependencies
Enables task dependencies validation.
The Gantt supports the following dependency validation rules:
- Finish to Start (FS) - A successor task's start point should be equal or later than the preceding task's end point.
- Start to Start (SS) - A successor task's start point should be equal or later than the preceding task's start point.
- Finish to Finish (FF) - A successor task's end point should be equal or later than the preceding task's end point.
- Start to Finish (SF) - A successor task's end point should be equal or later than a preceding task's start point.
The Gantt allows you to validate relationships between tasks when they are edited.
| User Action | Dependency Type | Gantt's Reaction | 
|---|---|---|
| Move a predecessor task (Task 1) to the left or right. | Finish to Start (FS):  Start to Start (SS):  Start to Finish (SF):  Finish to Finish (FF):  | The UI component moves a successor task (Task 2) forward or backward to the same time interval. | 
| Move a successor task (Task 2) to the left. | Finish to Start (FS):  Start to Start (SS):  Start to Finish (SF):  Finish to Finish (FF):  | This change is denied as it violates dependency rules. The control displays a popup window and suggests the following actions: 
 | 
| Move a successor task (Task 2) to the right. | Finish to Start (FS):  Start to Start (SS):  Start to Finish (SF):  Finish to Finish (FF):  | The control displays a popup window and suggests the following actions: 
 | 
If you have technical questions, please create a support ticket in the DevExpress Support Center.