Understanding ASP.NET Eval() and Bind()

Question

Can anyone show me some absolutely minimal ASP.NET code to understand Eval() and Bind()?

It is best if you provide me with two separate cod

Answer 1

The question was answered perfectly by Darin Dimitrov, but since ASP.NET 4.5, there is now a better way to set up these bindings to replace* Eval() and Bind(), taking advantage of the strongly-typed bindings.

*Note: this will only work if you're not using a SqlDataSource or an anonymous object. It requires a Strongly-typed object (from an EF model or any other class).

This code snippet shows how Eval and Bind would be used for a ListView control (InsertItem needs Bind, as explained by Darin Dimitrov above, and ItemTemplate is read-only (hence they're labels), so just needs an Eval):

    
        

            Title: 
         
            Description: 
        
                    
        
    
    
        

            Title: 

            Description: 
        
            
        
      

From ASP.NET 4.5+, data-bound controls have been extended with a new property ItemType, which points to the type of object you're assigning to its data source.

Picture is the strongly type object (from EF model). We then replace:

Bind(property) -> BindItem.property
Eval(property) -> Item.property

So this:

<%# Bind("Title") %>      
<%# Bind("Description") %>         
<%#  Eval("Title") %> 
<%# Eval("Description") %>

Would become this:

<%# BindItem.Title %>         
<%# BindItem.Description %>
<%# Item.Title %>
<%# Item.Description %>

Advantages over Eval & Bind:

• IntelliSense can find the correct property of the object your're working with
• If property is renamed/deleted, you will get an error before page is viewed in browser
• External tools (requires full versions of VS) will correctly rename item in markup when you rename a property on your object

Source: from this excellent book