// ✅ REQUIRED - Must match data property name exactly
<ejs-treegrid 
  [dataSource]='data'
  childMapping='subtasks'>  // Property name is case-sensitive
</ejs-treegrid>

// ❌ WRONG - Will not work
<ejs-treegrid 
  [dataSource]='data'>
  <!-- No expansion possible without childMapping -->
</ejs-treegrid>

// ✅ CORRECT - childMapping matches 'subtasks' property
public data = [
  {
    TaskID: 1,
    TaskName: 'Parent',
    subtasks: [  // Must match childMapping value
      { TaskID: 2, TaskName: 'Child' }
    ]
  }
];

// Alternative: Flat structure with parent IDs
<ejs-treegrid 
  [dataSource]='flatData'
  idMapping='TaskID'
  parentIdMapping='ParentID'
  hasChildMapping='isParent'>
</ejs-treegrid>

// ✅ CORRECT - Type matches column definition
public data = [
  {
    TaskID: 1,              // number type
    TaskName: 'Planning',   // string type
    StartDate: new Date(),  // Date object for date columns
  }
];

// Column definition must match data types
<e-columns>
  <e-column field='TaskID' headerText='ID' type='number'></e-column>
  <e-column field='TaskName' headerText='Task' type='text'></e-column>
  <e-column field='StartDate' headerText='Date' type='date' format='yMd'></e-column>
</e-columns>

// ❌ WRONG - Type mismatch
public data = [
  {
    TaskID: '1',            // String instead of number
    StartDate: '02/03/2024' // String instead of Date object
  }
];

import { Component, ViewChild } from '@angular/core';
import { TreeGridComponent } from '@syncfusion/ej2-angular-treegrid';
import { PageService, SortService, FilterService, EditService } from '@syncfusion/ej2-angular-treegrid';

@Component({
  selector: 'app-treegrid',
  template: `
    <ejs-treegrid 
      #treegrid
      [dataSource]='data'
      [childMapping]='childMapping'
      [allowPaging]='true'
      [allowSorting]='true'
      [allowFiltering]='true'
      <e-columns>
        <e-column field='TaskID' headerText='Task ID' width='90' isPrimaryKey='true'></e-column>
        <e-column field='TaskName' headerText='Task Name' width='200'></e-column>
      </e-columns>
    </ejs-treegrid>
  `,
  providers: [PageService, SortService, FilterService, EditService]
})
export class AppComponent {
  @ViewChild('treegrid') treegrid!: TreeGridComponent;

  public data: Object[] = [
    {
      TaskID: 1,
      TaskName: 'Planning',
      subtasks: [
        { TaskID: 2, TaskName: 'Scope', Duration: 4, Progress: 100 },
        { TaskID: 3, TaskName: 'Budget', Duration: 4, Progress: 100 }
      ]
    }
  ];
  
  public childMapping: string = 'subtasks';
  
  public editSettings = { mode: 'Cell', allowEditing: true, allowDeleting: true, allowAdding: true };
}

import { PageService, SortService, FilterService, EditService, ExcelExportService, PdfExportService,
  PrintService, AggregateService, ToolbarService } from '@syncfusion/ej2-angular-treegrid';

@Component({
  providers: [
    PageService, 
    SortService, 
    FilterService, 
    EditService,
    ExcelExportService,
    PdfExportService,
    PrintService,
    AggregateService,
    ToolbarService
  ]
})