ASP.NET Custom Server Controls: Cute ASP.NET TextBox Control - Handling the “PostBack” from “ViewState”

(Page 5 of 6 )

In the previous section, I already explained the “viewstate” and how to handle it in a very easy manner using a simple “text” property. This section explains the implementation of “postback” in our control.

As you know, in general, any server control in ASP.NET maintains its “state” even after a “postback.” The “postback” could occur in several ways, including by just clicking a “submit” button. Within our control, I would like to maintain the same. As I am already maintaining the “state” information through “viewsate,” I need to refresh (or place) the latest value (or information) within my control before the page gets disposed. This could be solved by implementing the interface “IPostBackDataHandler.” Let us consider the following code:

Public Function LoadPostData(ByVal postDataKey As String, ByVal postCollection As System.Collections.Specialized.
NameValueCollection) As Boolean Implements System.Web.UI.IPostBackDataHandler.LoadPostData

If Text <> postCollection(Me.UniqueID) Then

Text = postCollection(Me.UniqueID)

Return True

End If

Return False

End Function

Public Sub RaisePostDataChangedEvent() Implements System.Web.UI.IPostBackDataHandler.
RaisePostDataChangedEvent

End Sub

You can observe that we need to implement two methods, namely “LoadPostData” and “RaisePostDataChangedEvent.” Within the “LoadPostData,” I am comparing the value available in “viewstate” (“text” property) with the posted value (could be the same or modified value) to the server with an IF condition. If a user modifies the value, the posted value would be different and we will update the latest value back to the “viewstate” using the same “text” property.

What are “Return True” and “Return False”? When the posted values are different from our previous state values and, if we want raise any events (such as the “textchanged” event or others), we would return TRUE. This in turn executes the method “RaisePostDataChangedEvent” (currently I implemented nothing inside that, as there exist no events within my control). Returning “false” would not execute “RaisePostDataChangedEvent” at all. Actually in this scenario, I don’t need to return “true” at all, but it is just for your understanding.

Next: Is it cute? How can we make it cute? >>
 

More ASP.NET Articles
More By Jagadish Chaterjee

Comments On: ASP.NET Custom Server Controls: Cute ASP.NET TextBox Control

· Communicate with your network of business associates, agents, dealers and clients...    · Is your post, having any relation with my article? I hope this is not an...    · Hello guys, this is my article on creating a Cute ASP.NET textbox control. You can...   >>> Post your comment now!