Using GridView's Object-Relational Hierarchy with Telerik Open Access ORM

by Nikolay Diyanov

November 30, 2010 Productivity 0 Comments

In our previous blog post we showed how to use the new RadGridView Object-Relational Hierarchy with the Entity Framework. The same scenario can be easily implemented with Telerik OpenAccess ORM. The OpenAccess wizard for adding a new DomainModel will help us build the model of the well-known Northwind database in a few easy steps:

Once this is done, the auto-generation of the hierarchy is very simple and needs just a few lines of code. We only need the LINQ query to the root object used for a DataSource (in our case “Suppliers”) and then setting AutoGenerateHierarchy to true:

NorthwindEntities entities = new NorthwindEntities();

var query = from suppliers in entities.Suppliers select suppliers;

this.radGridView1.DataSource = query.ToList();

this.radGridView1.AutoGenerateHierarchy = true;

The result is self-explanatory:

Although this was nice and quick, this scenario does not take into account further presentation tweaking, because it was auto-generated. In cases when you need to fine-tune the visible data and its presentation, you will need to manually add the Object-Relational hierarchy. The key thing in this setup is to add a relation that contains only one ChildColumnNames, i.e. the name of the IEnumerable/IList property used for loading the second data level (which is always loaded on expand through lazy loading):

private void Form2_Load(object sender, EventArgs e)

{

NorthwindEntities entities = new NorthwindEntities();

var query = from customers in entities.Customers select customers;

GridViewTemplate childTemplate = CreateChildTemplate();

GridViewRelation relation = new GridViewRelation(this.radGridView1.MasterTemplate, childTemplate);

relation.ChildColumnNames.Add("Orders");

this.radGridView1.Relations.Add(relation);

this.radGridView1.DataSource = query.ToList();

}

private GridViewTemplate CreateChildTemplate()

{

GridViewTemplate childTemplate = new GridViewTemplate();

this.radGridView1.Templates.Add(childTemplate);

GridViewTextBoxColumn column = new GridViewTextBoxColumn("OrderDate");