How to use the ObjectDataSource as a DataSource, simple example
I thought I’d give an example on how to use the ObjectDataSource in a webpage.
A typical example could be listing states etc. This is fairly static data so it may be unnecessary to query a database for each request.
However, in this example we’ll use the Authors and their Books as an example.
This example will use and ObjectDataSource as a DataSource. The object will be returned by projecting Authors and Books into a new class via a LINQ query.
I use LINQ to Objects here but a database connection could be used as well.
So, let’s get down to it.
- Create a new WebSite, using Location: Filesystem works fine.
- Right click the added App_Code folder, Add New Item -> Class, name it BookShop.cs and replace the code with this.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
public class BookShop
{
List<Author> Authors = new List<Author>();
List<Book> Books = new List<Book>();
public BookShop()
{
CreateBooksAndAuthors();
}
// This will return all Authors to be used by the dropdown.
public List<Author> GetAuthors()
{
return Authors;
}
// Constructs a new list of BookAuthorItem for provided authorId and returns this to be used by the GridView.
public List<BookAuthorItem> GetBooksByAuthorId(string authorId)
{
var q = from b in Books
where b.AuthorId.Equals(authorId)
select new BookAuthorItem
{
BookId = b.BookId,
BookName = b.BookName,
AuthorName = Authors.First(x => x.AuthorId.Equals(authorId)).AuthorName,
AuthorAlias = Authors.First(x => x.AuthorId.Equals(authorId)).AuthorAlias
};
return q.ToList();
}
public class Author
{
public string AuthorId { get; set; }
public string AuthorName { get; set; }
public string AuthorAlias { get; set; }
}
public class Book
{
public string BookId { get; set; }
public string BookName { get; set; }
public string AuthorId { get; set; }
}
// We will project the query result into this class and return it to the calling client.
public class BookAuthorItem
{
public string BookId { get; set; }
public string BookName { get; set; }
public string AuthorName { get; set; }
public string AuthorAlias { get; set; }
}
private void CreateBooksAndAuthors()
{
// Create some books and authors.
Authors.Add(new Author { AuthorId = "1", AuthorName = "Steve Stevenson", AuthorAlias = "The great Steve" });
Authors.Add(new Author { AuthorId = "2", AuthorName = "Tom Tomson", AuthorAlias = "T.T." });
Authors.Add(new Author { AuthorId = "3", AuthorName = "Eric Ericson", AuthorAlias = "The Swede" });
Authors.Add(new Author { AuthorId = "4", AuthorName = "Paul Paulson" });
Books.Add(new Book { BookId = "1", BookName = "The great book", AuthorId = "1" });
Books.Add(new Book { BookId = "2", BookName = "Once upon a time", AuthorId = "1" });
Books.Add(new Book { BookId = "3", BookName = "Learning is doing", AuthorId = "2" });
Books.Add(new Book { BookId = "4", BookName = "The not so great book", AuthorId = "3" });
Books.Add(new Book { BookId = "5", BookName = "Summer is good", AuthorId = "3" });
Books.Add(new Book { BookId = "6", BookName = "Ah, you again!", AuthorId = "4" });
Books.Add(new Book { BookId = "7", BookName = "Book about cats", AuthorId = "4" });
Books.Add(new Book { BookId = "8", BookName = "My story", AuthorId = "4" });
}
}
- Now on the Default.aspx page, drop a DropDownList from the toolbox onto it.
- Select "Choose Data Source...".
- Select "<New Data Source>" from the "Select a datasource" dropdown.
- Select Object in the "Choose a Data Source Type" dialog, and then OK.
- Select BookShop in the "Choose a Business" dialog, and then Next.
- Select "GetAuthors" from the "Choose a method" dropdown, and then Finish.
- Select AuthorName as the data field to display in the DropDownList, select AuthorId as the datafield for the value of the DropDownList, and OK.
- Select the "Enable AutoPostback" checkbox.
- Now on the Default.aspx page, drop a GridView from the toolbox (Data section) onto it.
- Select "<New Data Source>" from the "Choose Data Source..." list
- Select Object in the "Choose a Data Source Type" dialog, and then OK.
- Select BookShop in the "Choose a Business" dialog, and then Next.
- Select "GetBooksByAuthorId" from the "Choose a method" dropdown, and then Next.
- Select "Control" in the "Parameter Source" dropdown and "DropDownList1" as the ControlID in the "Define Parameters" dialog, and Finish.
- That is all, your Default.aspx page should now have the following in the body of the source.
<body>
<form id="form1" runat="server">
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"
DataSourceID="ObjectDataSource1" DataTextField="AuthorName" DataValueField="AuthorId">
</asp:DropDownList>
<asp:ObjectDataSource ID="ObjectDataSource1" runat="server"
SelectMethod="GetAuthors" TypeName="BookShop">
</asp:ObjectDataSource>
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="ObjectDataSource2">
<Columns>
<asp:BoundField DataField="BookId" HeaderText="BookId"
SortExpression="BookId" />
<asp:BoundField DataField="BookName" HeaderText="BookName"
SortExpression="BookName" />
<asp:BoundField DataField="AuthorName" HeaderText="AuthorName"
SortExpression="AuthorName" />
<asp:BoundField DataField="AuthorAlias" HeaderText="AuthorAlias"
SortExpression="AuthorAlias" />
</Columns>
</asp:GridView>
<asp:ObjectDataSource ID="ObjectDataSource2" runat="server" SelectMethod="GetBooksByAuthorId" TypeName="BookShop">
<SelectParameters>
<asp:ControlParameter ControlID="DropDownList1" Name="authorId" PropertyName="SelectedValue" Type="String" />
</SelectParameters>
</asp:ObjectDataSource>
</form>
</body>
- Run the application, you should now be able to change the content of the GridView by selecting different authors with the DropDownList.
"ObjectDataSource Class"
https://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.objectdatasource.aspx
"Language-Integrated Query (LINQ) - Projection Operations"