autoostback roerty in windows form

I don't know if you are asking how to use a TextBox or how to use an AutoPostBack in a Windows Forms application. AutoPostBack is totally irrelevant to forms applications. Also note that the "" tag is also totally irrelevant to forms applications. If you are asking how to use a textbox then please look at the tutorials in this web site and if they don't help try to clarify your question.

AutoPostBack is event for dropdown, textbox etc in asp.net (C#),

<asp:TextBox AutoPostBack="true" ID="TextBox1" OnTextChanged="textbox_TextChanged" runat="server">asp:TextBox>

and also create "textbox_TextChanged" method in code file for generating event

Shyja, What is a AutoPostBack? 

Read more before moving ahead..

About the event of TextBox, use event TextChanged.

Right Click on TexBox, select properties, go to Events, will list all events related to control.