C# Inserting a timer in Windows Form
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I am creating Windows Form that will validate a text in the richtextbox and get errors depending on the requirements given. My only problem now is that every time the richtextbox changes the validation is being process, I mean every key press. How can I set a timer so that every time the user edit some text in the richtextbox it will wait for some seconds to validate the text, not just every key press they do. To be clear here is my code: 

	private void richTextBox1_TextChanged(object sender, EventArgs e)
			{
				listView1.Items.Clear();

				//Requirement.cs is a class where all the functions for formatting is placed.

				Requirement req_obj = new Requirement();
				req_obj.check_casing(richTextBox1, listView1, errors);
				req_obj.check_punctuation(richTextBox1, listView1, errors);
				req_obj.check_spacing(richTextBox1, listView1, errors);
				req_obj.check_abbreviation(richTextBox1, listView1, errors);
				req_obj.check_others(richTextBox1, listView1, errors);

				label2.Text = "Warning(s) found:" + req_obj.error_counter;

What's happening is that everytime the user changes something in the r.textbox it automatically validates every single key press. 
What I want is to set timer everytime the user will edit the text, after the user edit the text, timer counts 3 before it perform the specific process. 
How can I do that? thanks