我的解决方案(基于Leppie的提示):
Process p = new Process();
p.StartInfo.FileName = textFilename.Text;
p.StartInfo.Arguments = textArgument.Text;
p.StartInfo.UserName = textUsername.Text;
p.StartInfo.Domain = textDomain.Text;
p.StartInfo.Password = securePassword.SecureText;
p.StartInfo.LoadUserProfile = true;
p.StartInfo.UseShellExecute = false;
try {
p.Start();
} catch (Win32Exception ex) {
MessageBox.Show("Error:\r\n" + ex.Message);
}