If a text box contains text from a text document, how can I make it trigger an action?

Question

I am trying to make a serial key registration program. How do I make it so that if they type in a serial key from a text document in my resources an action will happen? I want it sonthat if someone types in a certain serial key that it is in a text document, and presses register, and action will be triggered.

Answer 1

In WinForms ist is very easy to create event handlers. In the forms designer select the serial key textbox. In the properties window switch to events by clicking the button with lightning symbol. Here you have the choice between many events. The TextChanged event is a good one. It fires each time a character is entered or deleted. Depending on what you want to do the different Key... events the Leave event or Validated or Validating events may be useful. If you are using a button, just double click on the button to get a handler for the Click event.

Double click in the empty field next to the event name. Visual Studio automatically creates an event handler for you.

Answer 2

Creating a program that checks if a certain TextBox entry is present in an embedded resource is pretty easy in .NET. But...

Note that .NET is not a good platform for this sort of thing altogether. Implementing it would be very easy compared to ensuring that no one can read your document/resource (which would contain all valid keys) with freely available software such as ILSpy

Also check this question.

A simple implementation could be something like this:

TextBox ValidationKey = new TextBox();

Binding the EventHandler:

ValidationKey.KeyPress += new KeyPressEventHandler(ValidationKey_KeyPress);

Implementation of the EventHandler:

private void ValidationKey_KeyPress(object sender, KeyPressEventArgs e)
{
    bool isKeyValid = MyResourceFile.Keys.Contains(ValidationKey.Text);
    MessageBox.Show(string.Format("Is it a valid key: {0}", isKeyValid.ToString()));
}

This is a very naïve implementation in that when the user enters just one character it is very likely to pass the test. You might want to use a RegExp or first check that the ValidationKey.Text.Length equals the length of your valid keys.