I don't know if i understood you well, but if you want to create directory in a web site using c# the System.IO.Directory class. as follow:
first get the actual directory that your site is allocated on the remote server
string onServerPath = Request.PhysicalApplicationPath;
second create the directory
if (!Directory.Exists(onServerPath + textBox1.Text))
{
Directory.CreateDirectory(onServerPath + textBox1.Text);
}
note:
that if the directory that contains the directory you are attempting to create
the containing directory will created first then the sub directory will be created.
Thanks,
Bassem