Textbox problem in asp.net(c#)

If you are posting the values of those two text boxes, then from the code behind you can get the values of them by using txtusername.Text and txtpassword.Text respectively.

If you are redirecting to another page on the click event, then to use the values on that page you will first need to store them somewhere such as the Session. Here's a simple example:

Code in the button's click event to store values in the session:

Session["username"] = txtusername.Text;
Session["password"] = txtpassword.Text;

Code used to get the values from the session on another page:

string username = (string)(Session["username"] ?? "");
string password = (string)(Session["password"] ?? "");

Here's a good reference for sessions: Exploring Session in ASP.NET[^]