TextBox AutoPostBack

Or another alternative is to use data binding... asuming you're using vs.net, use the following steps: 1. in design mode, right click TextBox1 ---> click properties ---> set AutoPostBack to true... 2. right click TextBox2 ---> click properties ---> click on the elipses of the DataBindings property... 3. click on the Text property of TextBox2 you want to bind ---> Click Custom binding expression ---> type TextBox1.Text 4. in your code behind (aspx.cs), in Page_Load write TextBox2.DataBind(); another way is: 1. in your aspx file, add the following attributes to your TextBox1 control: AutoPostBack="True" 2. add the following attribute to your TextBox2 control: Text="<%# TextBox1.Text %> 3. in your code behind (aspx.cs), in Page_Load write TextBox2.DataBind(); Thats it and you're done... Please note that if you want a "real time" change in TextBox2, you better use a client side event... hope this helps...