Dear,
the code below will do the job
if(TextBox1.Text && TextBox2.Text == "")
{
label1.Text = "Enter 1 of the fields";
}
else
{
Response.Redirect('page2.aspx");
}
this code works fine but instead you can use 2 requiredFieldValidators set their ControlToValidate property to each fields you have and set its Text property to "This field cannot be empty";
Happy coding