Difference between Eval and Bind - Data Binding Expressions in ASP.NET

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In simple words, the Eval function is used to define one-way binding (read only). The Bind function is used for two-way binding (read-write)

So in a control like the GridView or the FormView, when you have to display read only data using a label control, you would be using the Eval function whereas when you want to update a database field, you would be using a TextBox and thus using the Bind function.

Note: You can use the Bind function to retrieve the value of a databound field, just as Eval does.

Here’s an example:

<asp:FormView ID="FormView1" runat="server"
 AllowPaging="True"
 DataKeyNames="CustomerID"
 DataSourceID="SqlDataSource1">       
     <EditItemTemplate>
         CustomerName:
         <asp:TextBox ID="txtCustName"
             runat="server"
             Text='<%# Bind("CName") %>'>
         </asp:TextBox>
     </EditItemTemplate>
    
     <ItemTemplate>
         CustID:
         <asp:Label ID="lblCustID"
             runat="server"
             Text='<%# Eval("CID") %>'>
         </asp:Label>
     </ItemTemplate>
 </asp:FormView>

You can read more on the Eval and Bind functions

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About The Author

Suprotim Agarwal, Developer Technologies MVP (Microsoft Most Valuable Professional) is the founder and contributor for DevCurry, DotNetCurry and SQLServerCurry. He is the Chief Editor of a Developer Magazine called DNC Magazine. He has also authored two Books - 51 Recipes using jQuery with ASP.NET Controls. and The Absolutely Awesome jQuery CookBook.

Follow him on twitter @suprotimagarwal.