Everyone knows what a login system is ! so i don't think any explanations are needed . i will come to the main thing , Today we are going to make a simple login system in c# .
You need two text boxes,two labels and two buttons.
Now make the controls look like this on form.

Now let's go for login button codes
//if textbox1 text is admin and textbox2 text is 1234567
if ((textBox1.Text == "admin") && (textBox2.Text == "1234567"))
{
//then show form2
Form2 nextform = new Form2();
nextform.ShowDialog();
}
else
{
//if username and password is incorrect show this message box
MessageBox.Show("Username or Password Invalid");
}
This is the code for button 2 which is a exit button
Application.Exit();
Alright we are done ! I hope this is helpful !