How can WinForm determine the number of characters in a text box?

You can use the Text property to get the number of characters in the text box, and then use the Length property to get the length of the string, which is the number of characters. Here is an example code:

int charCount = textBox1.Text.Length;

In this example, textBox1 is the name of your text box control. By accessing the Text property and using the Length property, you can get the number of characters in the text box. You can compare this number with the maximum character count required to perform the necessary action.